Physical quantity measurement device having a flow channel partition not directly exposed to the flow through the inflow port

ABSTRACT

A physical quantity measurement device measures a physical quantity of a fluid. The device includes a passage flow channel, a branch flow channel, a flow channel partition portion that separates the passage flow channel and the branch flow channel to have the branch flow channel branch off from the passage flow channel, and a physical quantity detector. The flow channel partition portion has a partition top portion as an upstream-side end that is not exposed through the inflow port.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of international PatentApplication No. PCT/JP2018/010140 filed on Mar. 15, 2018, whichdesignated the U.S. and claims the benefit of priority from JapanesePatent Application No. 2017-079879 filed on Apr. 13, 2017. The entiredisclosure of all of the above applications are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to a physical quantity measurementdevice.

BACKGROUND ART

As a physical quantity measurement device for measuring a physicalquantity of a fluid, for example, a physical quantity measurement devicefor measuring a flow rate of an intake air taken into an internalcombustion engine is known. The physical quantity measurement device hasa discharge passage for discharging the inflow fluid, and a branchpassage branched from the discharge passage, and a flow rate detectionunit is provided in the branch passage. While the branch passage iscurved to make one turn, the discharge passage is not greatly curved. Inthis example, a foreign matter having a relatively large mass of theforeign matter flowing into the discharge passage together with thefluid tends to move linearly as compared with the fluid. For thatreason, the foreign matter having the relatively large mass tends to bedischarged from an outflow port of the discharge passage withoutentering the branch passage. As a result, the detection accuracy of theflow rate detection unit is inhibited from being lowered by the presenceof the foreign matter.

SUMMARY

A first aspect of the present disclosure is a physical quantitymeasurement device that measures a physical quantity of a fluid. Thedevice includes a passage flow channel that includes an inflow port andan outflow port, the fluid entering the passage flow channel through theinflow port and exiting the passage flow channel through the outflowport, a branch flow channel that branches off from the passage flowchannel, a flow channel partition portion that separates the passageflow channel and the branch flow channel to have the branch flow channelbranch off from the passage flow channel, and a physical quantitydetector that detects the physical quantity of the fluid in the branchflow channel, wherein the flow channel partition portion has a partitiontop portion as an upstream-side end that is not exposed through theinflow port.

A second aspect of the present disclosure is a physical quantitymeasurement device that measures a physical quantity of a fluid. Thedevice includes a passage flow channel having an inflow port and anoutflow port, the fluid entering the passage flow channel through theinflow port and exiting the passage flow channel through the outflowport, a branch flow channel that branches off from the passage flowchannel, a flow channel partition that separates the passage flowchannel and the branch flow channel to have the branch flow channelbranch off from the passage flow channel, and a physical quantitydetector that detects the physical quantity of the fluid in the branchflow channel, wherein a pair of opposing surfaces in an inner peripheralsurface of the passage flow channel face each other across the inflowport and a flow channel boundary portion that is a boundary between thepassage flow channel and the branch flow channel, a direction alongwhich the pair of opposing surfaces are arranged is defined as a widthdirection, a direction orthogonal to the width direction and orthogonalto an inflow direction of the fluid through the inflow port is definedas a height direction, a surface of the inner peripheral surface of thepassage flow channel on the same side as the flow channel boundaryportion in the height direction is defined as a ceiling surface, asurface of the inner peripheral surface of the passage flow channelopposite to the ceiling surface in the height direction is defined as abottom surface, a virtual line that passes through both a tip portion ofa ceiling projection portion protruding from the ceiling surface towardthe bottom surface and a tip portion of a bottom projection portionprotruding from the bottom surface toward the ceiling surface on anupstream side of the flow channel boundary portion is defined as aconnecting line, wherein the connecting line causes a connecting angle,which is a virtual angle formed between the inflow direction and theconnecting line, facing toward the ceiling surface, and having the tipportion of the ceiling projection portion as a vertex, to have a maximumvalue, an angle that is formed between the connecting line and the flowchannel partition portion at an intersection point between theconnection line and the flow channel partition portion and faces awayfrom the branch flow channel is defined as an intersection angle, andthe intersection angle is greater than 90 degrees.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects, features and advantages of the presentdisclosure will become more apparent from the following detaileddescription made with reference to the accompanying drawings.

The above and other objects, features and advantages of the presentdisclosure will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a front view of an air flow meter in a state of being attachedto an intake pipe as viewed from an upstream side according to a firstembodiment.

FIG. 2 is a cross-sectional view taken along a line II-II of FIG. 1.

FIG. 3 is a diagram a periphery of a passage flow channel in FIG. 2.

FIG. 4 is a diagram illustrating a configuration in which a ceilingsurface of the passage flow channel does not have a step surface, unlikethe first embodiment.

FIG. 5 is a front view of an air flow meter attached to an intake pipeas viewed from an upstream side according to a second embodiment.

FIG. 6 is a view showing a configuration of a housing main body in astate in which a back cover in FIG. 5 is removed.

FIG. 7 is a view showing a configuration of a housing main body in astate in which a front cover in FIG. 5 is removed.

FIG. 8 is a diagram the periphery of a passage flow channel in FIG. 6.

FIG. 9 is an enlarged view of the periphery of a step surface.

FIG. 10 is a diagram illustrating a configuration in which a ceilingsurface of the passage flow channel has no inflow step surface, unlikethe second embodiment.

FIG. 11 is an enlarged view of the periphery of a step surface in amodification B1.

FIG. 12 is an enlarged view of the periphery of the step surface in themodification B1.

FIG. 13 is an enlarged view of the periphery of a step surface in amodification B3.

FIG. 14 is an enlarged view of the periphery of a step surface in amodification B4.

FIG. 15 is a diagram of the periphery of a passage flow channel in amodification B5.

FIG. 16 is a diagram illustrating a configuration in which the ceilingsurface of the passage flow channel has no outflow step surface, unlikethe modification B5.

FIG. 17 is a diagram of the periphery of the passage flow channel in amodification B6.

FIG. 18 is a diagram of the periphery of a passage flow channel in amodification B7.

FIG. 19 is a diagram of the periphery of a passage flow channel in amodification B8.

FIG. 20 is a diagram of the periphery of a passage flow channel in amodification B9.

FIG. 21 is a diagram of the periphery of a passage flow channel in amodification B10.

FIG. 22 is a diagram of the periphery of a passage flow channel in amodification B11.

FIG. 23 is a diagram of the periphery of a passage flow channelaccording to a third embodiment.

FIG. 24 is a diagram of the vicinity of an inflow port of an air flowmeter as viewed from an upstream side.

FIG. 25 is a diagram of the vicinity of an outflow port of the air flowmeter as viewed from a downstream side.

FIG. 26 is a diagram illustrating a configuration in which the air flowmeter has no inflow restriction portion, unlike the third embodiment.

FIG. 27 is a diagram of the periphery of a passage flow channel in amodification C1.

FIG. 28 is a diagram of the periphery of a passage flow channel in amodification C2.

FIG. 29 is a diagram of the periphery of a passage flow channel in amodification C3.

FIG. 30 is a diagram of the periphery of a passage flow channel inmodifications C4 and C5.

FIG. 31 is a diagram of the periphery of the passage flow channel in themodification C5.

FIG. 32 is a cross-sectional view of a passage flow channel as viewedfrom a bottom side toward a ceiling side in a direction orthogonal to aheight direction in a modification C6.

FIG. 33 is a diagram of the periphery of a passage flow channelaccording to a fourth embodiment.

FIG. 34 is a diagram illustrating an traveling direction of a largeforeign matter.

FIG. 35 is a diagram illustrating a configuration in which a partitiontop portion is exposed to the upstream side from an inflow port, unlikethe fourth embodiment.

FIG. 36 is a diagram of the periphery of a passage flow channel in amodification D1.

FIG. 37 is a diagram of the periphery of a passage flow channel in amodification D3.

FIG. 38 is a diagram of the periphery of a passage flow channel in amodification D4.

FIG. 39 is a diagram of the periphery of a passage flow channel in amodification D6.

FIG. 40 is a diagram illustrating how a large foreign matter advances.

FIG. 41 is a diagram of the periphery of a passage flow channel in amodification D7.

FIG. 42 is a diagram of the periphery of a passage flow channelaccording to a fifth embodiment.

FIG. 43 is a diagram of the vicinity of the inflow port of the air flowmeter as viewed from the upstream side.

FIG. 44 is a diagram illustrating an inflow region and a lateral region.

FIG. 45 is a diagram illustrating how a large foreign matter advances.

FIG. 46 is a diagram of the periphery of a passage flow channel in amodification E3.

FIG. 47 is a diagram illustrating a positional relationship between theinflow region, the lateral region, and an guiding surface.

FIG. 48 is a diagram of the periphery of a passage flow channel in amodification E4.

FIG. 49 is a diagram illustrating a positional relationship between theinflow region, the lateral region, and the guiding surface.

FIG. 50 is a diagram of the periphery of a passage flow channel in amodification E5.

FIG. 51 is a diagram illustrating a cover portion in a modification E6.

FIG. 52 is a diagram illustrating how a large foreign matter advances.

FIG. 53 is a diagram illustrating how a large foreign matter advances ina modification E7.

FIG. 54 is a diagram of the periphery of a passage flow channel in asixth embodiment.

FIG. 55 is a cross-sectional view of the passage flow channel as viewedfrom a bottom side toward a ceiling side in a direction orthogonal tothe height direction.

FIG. 56 is a diagram illustrating the inflow region and the lateralregion.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a plurality of embodiments of the present disclosure willbe described with reference to the drawings. Incidentally, the samereference numerals are assigned to the corresponding components in eachembodiment, and thus, duplicate descriptions may be omitted. When only apart of the configuration is described in each embodiment, theconfiguration of the other embodiments described above can be applied tothe other parts of the configuration. Further, not only the combinationsof the configurations explicitly shown in the description of therespective embodiments, but also the configurations of the plurality ofembodiments can be partially combined with each other even if thecombinations are not explicitly shown if there is no problem in thecombination in particular. Unspecified combinations of theconfigurations described in the plurality of embodiments and themodification examples are also disclosed in the following description.

In a conventional physical quantity measurement device as describedabove, even if the foreign matter easily travels linearly, the foreignmatter does not necessarily enter the branch passage, and there is roomfor an improvement in the configuration in which the foreign matter doesnot enter the branch passage. In other words, there is room for animprovement in the configuration for reducing an arrival of the foreignmatter to the physical quantity detector such as the flow rate detectionunit.

First Embodiment

An air flow meter 10 shown in FIGS. 1 and 2 is a physical quantitymeasurement device that measures a physical quantity such as a flowrate, a temperature, a humidity, and a pressure with respect to a fluidsuch as air. The air flow meter 10 is mounted on a vehicle having aninternal combustion engine 11 such as an engine. The internal combustionengine 11 has an intake passage 12 and an exhaust passage, and the airflow meter 10 is attached to the intake passage 12. In that case, thefluid to be measured by the air flow meter 10 is an intake air flowingthrough the intake passage 12. The intake air is a gas to be supplied toa combustion chamber of the internal combustion engine 11. The air flowmeter 10 is disposed on a downstream side of an air cleaner in theintake passage 12. In that case, in the intake passage 12, the aircleaner is at the upstream side and the combustion chamber is at thedownstream side relative to the air flow meter 10.

The air flow meter 10 is detachably attached to an intake pipe 12 adefining the intake passage 12. The air flow meter 10 is inserted into asensor insertion hole 12 b provided to penetrate through a cylindricalwall of the intake pipe 12 a, and is at least partially positioned inthe intake passage 12. The intake pipe 12 a has a flange portion 12 cextending from the sensor insertion hole 12 b toward an outer peripheralside. The flange portion 12 c extends along a peripheral portion of thesensor insertion hole 12 b, and is, for example, ring-shaped. A tip endface of the flange portion 12 c extends in a direction orthogonal to acenter line of the flange portion 12 c. In that case, the tip end faceof the flange portion 12 c extends in a longitudinal direction of theintake passage 12, that is, in a direction in which an intake air flowsin the intake passage 12.

The air flow meter 10 includes a housing 21 and a flow rate detectionunit 22. The housing 21 is made of, for example, a resin material or thelike. In the air flow meter 10, since the housing 21 is attached to theintake pipe 12 a, the flow rate detection unit 22 is brought into astate in which the flow rate detection unit 22 can come into contactwith the intake air flowing through the intake passage 12. The housing21 has a flow channel forming portion 24, a fitting portion 25, anO-ring 26, a flange portion 27, and a connector portion 28.

The flow channel forming portion 24 defines flow channels 31 and 32. Theflow channels 31 and 32 are provided by an internal space of the flowchannel forming portion 24, and introduce a part of the intake airflowing through the intake passage 12 into the housing 21. The passageflow channel 31 penetrates through the flow channel forming portion 24,and an upstream end portion of the passage flow channel 31 is referredto as an inflow port 33 a, and a downstream-side end portion of thepassage flow channel 31 is referred to as an outflow port 33 b. Themeasurement flow channel 32 is a branch flow channel that branches offfrom an intermediate portion of the passage flow channel 31, and has acurved portion to circulate around the inside of the flow channelforming portion 24. However, the measurement flow channel 32 does notmake one turn, and a portion close to the upstream end portion and aportion close to the downstream end portion of the measurement flowchannel 32 do not overlap with each other in the width direction of theflow channel forming portion 24. Also, the passage flow channel 31 andthe measurement flow channel 32 do not overlap with each other in thewidth direction of the flow channel forming portion 24.

The downstream end portion of the measurement flow channel 32 is openedsimilarly to the downstream-side end portion of the passage flow channel31, and the downstream-side end portion is referred to as a measurementoutlet 33 c. The measurement flow channel 32 branches toward thedownstream end portion, and thus has two measurement outlets 33 c, andthose measurement outlets 33 c are disposed laterally at positionsspaced apart from each other in the width direction of the flow channelforming portion 24. As described above, because the passage flow channel31 and the measurement flow channel 32 do not overlap with each other inthe width direction of the flow channel forming portion 24, each of themeasurement outlets 33 c and the outflow port 33 b do not overlap witheach other in the width direction of the flow channel forming portion24. The intake passage 12 may be referred to as a main passage, and thepassage flow channel 31 and the measurement flow channel 32 may becollectively referred to as a secondary passage. The measurement outlet33 c corresponds to a branch outlet.

The fitting portion 25 is a portion that is fitted into the sensorinsertion hole 12 b through the O-ring 26. The O-ring 26 is a member forsealing the intake passage 12 and the outside of the intake pipe 12 a.The O-ring 26 is externally fitted to the fitting portion 25, and isinterposed between the fitting portion 25 and the sensor insertion hole12 b in a state of entering the inner peripheral side of the flangeportion 12 c. The flange portion 27 is disposed on a side opposite tothe flow channel forming portion 24 across the fitting portion 25, andcovers the sensor insertion hole 12 b from an outer peripheral side ofthe intake pipe 12 a. The flange portion 27 is caught by the tip portionof the flange portion 12 c of the intake pipe 12 a to restrict thehousing 21 from excessively entering the intake passage 12. The flangeportion 27 has a flange surface 27 a which faces the flow channelforming portion 24. The flange surface 27 a extends in parallel with thetip end face of the flange portion 12 c, and is put on the tip end faceof the flange portion 12 c.

The connector portion 28 surrounds multiple terminals. A plug portion isinserted into the connector portion 28. The plug portion is provided atan end portion of a connecting line electrically connected directly orindirectly to an engine control device such as an ECU, and mates withthe connector portion 28.

The flow rate detection unit 22 is a thermal type flow rate sensorusing, for example, a heat generation unit such as a heat generatingresistive element or a heater unit and a detection surface of the flowrate detection unit 22 is formed of a membrane.

The flow rate detection unit 22 is disposed at an intermediate positionof the measurement flow channel 32. When the housing 21 is attached tothe intake pipe 12 a, the intake air flowing through the measurementflow channel 32 is supplied to the flow rate detection unit 22. The flowrate detection unit 22 is electrically connected to the multipleterminals provided in the connector portion 28. The flow rate detectionunit 22 outputs a sensor signal corresponding to the intake flow rateand corresponding to a flow rate of the air flowing through themeasurement flow channel 32 to the engine control device as a flow ratesignal. The flow rate detection unit 22 detects the flow rate of theintake air flowing in the intake passage 12 by detecting the flow rateof the intake air flowing in the measurement flow channel 32. The flowrate detection unit 22 corresponds to a “physical quantity detector”that detects the flow rate of the intake air as a physical quantity.Further, the flow rate detection unit 22 is not limited to the thermaltype flow rate sensor, and may be a movable flap type flow rate sensor,a Kalman vortex type flow rate sensor, or the like.

The air flow meter 10 has a temperature detection unit for detecting atemperature and a humidity detection unit for detecting a humidity inaddition to the flow rate detection unit 22. The temperature detectionunit and the humidity detection unit are provided on an outer peripheralside of the housing 21, and output sensor signals corresponding to thetemperature and humidity of the intake air flowing through the intakepassage 12 as a temperature signal and a humidity signal. For example,the air flow meter 10 has a support for supporting those detection unitson the outer peripheral side of the housing 21, and the support is fixedto the housing 21.

In the air flow meter 10, a direction in which the two measurementoutlets 33 c are aligned is referred to as a width direction X, adirection in which the flow channel forming portion 24 and the flangeportion 27 are aligned is referred to as a height direction Y, and adirection in which the passage flow channel 31 extends is referred to asa depth direction Z. The width direction X, the height direction Y, andthe depth direction Z are orthogonal to each other, and the flangesurface 27 a of the flange portion 27 extends in parallel to both thewidth direction X and the depth direction Z. In a state in which the airflow meter 10 is attached to the intake pipe 12 a, the inflow port 33 afaces the upstream side of the intake passage 12, and the outflow port33 b and the measurement outlet 33 c face the downstream side. In thatcase, it is considered that the direction in which the intake air flowsin the intake passage 12 is the depth direction Z, and the inflowdirection of the inflow air from the inflow port 33 a is likely to bethe same as the depth direction Z. In the air flow meter 10, the intakeair flowing in from the inflow port 33 a passes through the passage flowchannel 31 and the measurement flow channel 32, and flows out from theoutflow port 33 b and each measurement outlet 33 c.

In a flow channel boundary portion 34, which is a boundary between thepassage flow channel 31 and the measurement flow channel 32, anintermediate portion of the passage flow channel 31 is opened toward theflange portion 27 in the height direction Y. In the flow channelboundary portion 34, the intermediate portion of the passage flowchannel 31 and the upstream end portion of the measurement flow channel32 are connected to each other, and the upstream end portion of themeasurement flow channel 32 can also be referred to as a measurementinlet. The measurement flow channel 32 has a portion extending in thedepth direction Z between the flow channel boundary portion 34 and themeasurement outlet 33 c, and the flow rate detection unit 22 is disposedin that portion.

In the air flow meter 10, it is assumed that dust such as sand and dustenters from the inflow port 33 a as foreign matter together with intakeair. In that case, it is considered that most of the foreign mattertravels in the depth direction Z along a flow of the intake air to exitfrom the outflow port 33 b, but some of the foreign matter enters themeasurement flow channel 32 together with some of the intake air. Inparticular, it is considered that a large foreign matter such as aforeign matter having a relatively large mass or a foreign matter havinga relatively large size tends to move linearly regardless of the flowdirection of the intake air. For that reason, there is a concern thatthe large foreign matter collides with an inner peripheral surface 31 aof the passage flow channel 31 and rebounds, and when a travelingdirection of the large foreign matter changes, the large foreign mattermore easily enters the measurement flow channel 32.

On the other hand, in the present embodiment, the large foreign matterthat has rebounded on the inner peripheral surface 31 a of the passageflow channel 31 is inhibited from entering the measurement flow channel32. It is considered that a small foreign matter, such as a foreignmatter having a relatively small mass or a foreign matter having arelatively small size, tends to change the traveling direction of thesmall foreign matter in accordance with the flow of intake air, andtends to bend before colliding with the inner peripheral surface 31 a ofthe passage flow channel 31.

As shown in FIGS. 1 and 3, the inner peripheral surface 31 a of thepassage flow channel 31 has a ceiling surface 36, a bottom surface 37,and a pair of wall surfaces 38. The pair of wall surfaces 38 are a pairof facing surfaces facing each other across the flow channel boundaryportion 34, the inflow port 33 a, and the outflow port 33 b in the widthdirection X, and the ceiling surface 36 and the bottom surface 37 are apair of facing surfaces facing each other across the wall surfaces 38.In the passage flow channel 31, a portion of the ceiling surface 36 isopened, and an upstream end portion of the measurement flow channel 32is connected to the opened portion, thereby providing the flow channelboundary portion 34. The ceiling surface 36 has an inflow ceilingsurface portion 36 a between the inflow port 33 a and the flow channelboundary portion 34, and an outflow ceiling surface portion 36 b betweenthe flow channel boundary portion 34 and the outflow port 33 b.

In this example, the flow channel boundary portion 34 has an upstreamboundary portion 34 a located at the most upstream side and a downstreamboundary portion 34 b located at the most downstream side, and in theheight direction Y, the upstream boundary portion 34 a is located at aposition spaced apart from the flange portion 27 from the downstreamboundary portion 34 b. In that case, the upstream end portion of themeasurement flow channel 32 is opened not toward the inflow port 33 abut toward the outflow port 33 b. For that reason, even if the foreignmatter traveling linearly in the depth direction Z enters from theinflow port 33 a, the foreign matter does not easily enter themeasurement flow channel 32 as it is. In the above configuration, forexample, even if a person looks into the passage flow channel 31 fromthe inflow port 33 a in the depth direction Z, an upstream end portionof the measurement flow channel 32 cannot be visualized.

In the ceiling surface 36, since the inflow ceiling surface portion 36 aand the outflow ceiling surface portion 36 b have step surfaces 41 a and41 b and connection surfaces 42 a and 42 b, respectively, a step facingthe inflow port 33 a is defined. In the inflow ceiling surface portion36 a, the multiple inflow step surfaces 41 a are disposed at depthintervals Da along the aligned direction of the inflow port 33 a and theflow channel boundary portion 34. In the outflow ceiling surface portion36 b, the multiple outflow step surfaces 41 b are aligned at depthintervals Db along the alignment direction of the flow channel boundaryportion 34 and the outflow port 33 b, and the depth interval Db issmaller than a depth interval Da. The step surfaces 41 a and 41 b extendtoward the bottom surface 37 on the ceiling surface 36, and thus facethe inflow port 33 a, and extend over the pair of wall surfaces 38. Eachinflow step surface 41 a and each outflow step surface 41 b extend inthe same direction, specifically, both extend in a direction orthogonalto the depth direction Z.

The inflow connection surfaces 42 a connect the downstream-side endportion of the upstream side inflow step surface 41 a and the upstreamend portion of the downstream side inflow step surface 41 a in theadjacent inflow step surfaces 41 a at the inflow ceiling surface portion36 a, and the multiple inflow connection surfaces 42 a are providedaccording to the number of the inflow step surface 41 a. The outflowconnection surfaces 42 b connect the downstream-side end portion of theupstream side outflow step surface 41 b and the upstream end portion ofthe downstream side outflow step surface 41 b in the adjacent outflowstep surfaces 41 b at the outflow ceiling surface portion 36 b, and themultiple outflow connection surfaces 42 b are provided according to thenumber of the outflow step surface 41 b. The connection surfaces 42 aand 42 b extend in the same direction, specifically, in a directionorthogonal to the height direction Y. In other words, each inflowconnection surface 42 a is orthogonal to the inflow step surface 41 a,and each outflow connection surface 42 b is orthogonal to the outflowstep surface 41 b. In that case, in the depth direction Z, the depthdimensions of the connection surfaces 42 a and 42 b are the same as thedepth intervals Da and Db of the adjacent step surfaces 41 a and 41 b.

The inflow ceiling surface portion 36 a and the outflow ceiling surfaceportion 36 b are formed in a staircase shape as a whole by the stepsurfaces 41 a and 41 b and the connection surfaces 42 a and 42 a. In theinflow ceiling surface portion 36 a, the step gradually increases towardthe downstream side. Specifically, while the depth interval Da isuniform in each step, a height dimension Ha of the inflow step surface41 a along the height direction Y gradually increases as a distance fromthe inflow port 33 a increases. In the step close to the inflow port 33a, the height dimension Ha is smaller than the depth interval Da, but adifference between the height dimension Ha and the depth interval Dagradually decreases as the step comes closer to the flow channelboundary portion 34, and in the step close to the flow channel boundaryportion 34, the height dimension Ha and the depth interval Da havesubstantially the same value. A height dimension Ha may be smaller thanthe depth interval Da.

On the other hand, in the outflow ceiling surface portion 36 b, the stepbecomes gradually smaller toward the downstream side. Specifically,while the depth interval Db is uniform in each step, a height dimensionHb of the outflow step surface 41 b in the height direction Y graduallydecreases as the step comes closer to the outflow port 33 b. In the stepclose to the flow channel boundary portion 34, the height dimension Hbis larger than the depth interval Db, but the difference between theheight dimension Hb and the depth interval Db gradually decreases as thestep comes closer to the flow outflow port 33 b, and in the step closerto the flow outflow port 33 b, the height dimension Hb is larger thanthe depth interval Db.

In the ceiling surface 36, the overall inclination angle of the outflowceiling surface portion 36 b with respect to the depth direction Z islarger than the overall inclination angle of the inflow ceiling surfaceportion 36 a with respect to the depth direction Z. In this example, ina positional relationship between the upstream end portion and thedownstream end portion of the inflow ceiling surface portion 36 a, aseparation distance in the height direction Y is referred to as a heightdistance Hay, and a separation distance in the depth direction Z isreferred to as a depth distance Daz. In a positional relationshipbetween the upstream end portion and the downstream end portion of theinflow ceiling surface portion 36 a, a separation distance in the heightdirection Y is referred to as a height distance Hby, and a separationdistance in the depth direction Z is referred to as a depth distanceDaz. In that instance, a value of Hby/Dbz indicating the degree ofinclination of the outflow ceiling surface portion 36 b is larger than avalue of Hay/Daz indicating the degree of inclination of the inflowceiling surface portion 36 a. As a result, the intake air easily flowsin from the inflow port 33 a, and a flow rate of the intake air in themeasurement flow channel 32 easily increases.

The inflow ceiling surface portion 36 a is curved so that anintermediate portion in the width direction X swells toward the flangeportion 27 in accordance with the shape of the inflow port 33 a. In thatcase, both the upstream end portion and the downstream-side end portionof the inflow step surface 41 a are curved. The inflow connectionsurfaces 42 a are curved so as to connect the adjacent inflow stepsurfaces 41 a to each other. On the other hand, the outflow port 33 bhas a substantially rectangular shape, and the outflow ceiling surfaceportion 36 b is not curved.

According to the present embodiment described so far, since the inflowceiling surface portion 36 a has the inflow step surfaces 41 a, aforeign matter that has entered from the inflow port 33 a hardly entersthe measurement flow channel 32. For example, as indicated by a solidline in FIG. 3, when a large foreign matter F1 entering from the inflowport 33 a travels linearly in the depth direction Z and collides withthe inflow step surface 41 a of the inflow ceiling surface portion 36 a,there is a high possibility that the large foreign matter F1 returnsback to the inflow port 33 a so as to follow its own trajectory. Asdescribed above, the large foreign matter F1 does not easily advance tothe downstream side by colliding with the inflow step surface 41 a ofthe inflow ceiling surface portion 36 a in the passage flow channel 31,and does not easily enter the measurement flow channel 32.

On the other hand, unlike the present embodiment, for example, in aconfiguration in which the inflow ceiling surface portion 36 a does nothave the inflow step surface 41 a as shown in FIG. 4, the inflow ceilingsurface portion 36 a is not orthogonal to the depth direction Z. Forthat reason, it is conceivable that the large foreign matter F1 collideswith the inflow ceiling surface portion 36 a which is inclined as awhole, and advances to the downstream side while changing the travelingdirection. In that case, there is a concern that the large foreignmatter F1 can easily enter the measurement flow channel 32 by advancingdownstream while the large foreign matter F1 rebounds at the bottomsurface 37 following the inflow ceiling surface portion 36 a, asindicated by a solid line in FIG. 4, depending on an angle at which thelarge foreign matter F1 rebounds at the inflow ceiling portion 36 a. Asdescribed above, when the traveling direction of the large foreignmatter F1 changes in the height direction Y with the rebound at theinflow ceiling surface portion 36 a, the possibility that the largeforeign matter F1 flows into the measurement flow channel 32 is likelyto increase. In that regard, according to the present embodiment, sincea configuration is realized in which the traveling direction of thelarge foreign matter F1 rebounded at the inflow step surface 41 a of theinflow ceiling surface portion 36 a does not easily change in the heightdirection Y, the large foreign matter F1 can be inhibited from easilyentering the measurement flow channel 32.

In the air flow meter 10 in which the flow rate detection unit 22 isprovided in the measurement flow channel 32, if the flow rate of theintake air flowing through the measurement flow channel 32 is too small,there is a concern that the detection accuracy of the flow ratedetection unit 22 is lowered. On the other hand, according to thepresent embodiment, since the multiple inflow step surfaces 41 a arealigned in the depth direction Z, the cross-sectional area of thepassage flow channel 31 can be gradually reduced toward the flow channelboundary portion 34 while increasing the open area of the inflow port 33a as much as possible. For that reason, the inflow of the intake airinto the measurement flow channel 32 can be inhibited from beinginsufficient while inhibiting the inflow of the large foreign matterinto the measurement flow channel 32 by the inflow step surface 41 a.

According to the present embodiment, since the multiple inflow stepsurfaces 41 a are included in the inflow ceiling surface portion 36 a,the inflow ceiling surface portion 36 a can be gradually spaced apartfrom the flange portion 27 as the inflow ceiling surface portion 36 acomes closer to the flow channel boundary portion 34 from the inflowport 33 a. In that case, for example, as shown in FIG. 3, since theintake air G flowing in from the inflow port 33 a tends to graduallymove away from the flow channel boundary portion 34 in the Y-direction,the small foreign matter that is easily susceptible to the flow of theintake air G can be inhibited from flowing into the measurement flowchannel 32 in addition to the large foreign matter.

According to the present embodiment, since the height dimension Ha ofthe passage flow channel 31 increases more as the inflow step surface 41a is closer to the flow channel boundary portion 34, the change rate inthe traveling direction of the intake air flowing in from the inflowport 33 a can be gradually increased. In that case, as compared with thecase where the change rate in the traveling direction of the intake airis abruptly increased, the flow of the intake air is hardly disturbed bythe generation of a vortex or the like. For that reason, the flow rateof the intake air in the measurement flow channel 32 can be inhibitedfrom being insufficient due to the intake air hardly flowing into themeasurement flow channel 32 due to the turbulence of the flow, or theforeign matter entrained by the turbulence of the flow can be inhibitedfrom entering the measurement flow channel 32.

According to the present embodiment, the inflow connection surface 42 aextends in parallel with the depth direction Z. For that reason, theinflow connection surface 42 a can be inhibited from becoming anobstacle to the foreign matter when the foreign matter entering from theinflow port 33 a and traveling linearly in the depth direction Z reachesthe inflow step surface 41 a.

According to the present embodiment, since the inflow step surface 41 aextends in parallel with the height direction Y, the inflow step surface41 a is orthogonal to the depth direction Z in which the intake aireasily enters from the inflow port 33 a. This makes it possible toinhibit that the foreign matter, which collides with the inflow stepsurface 41 a and rebounds, advances to the downstream side in thedirection inclined with respect to the height direction Y, collides withthe bottom surface 37, and rebounds to enter the measurement flowchannel 32.

According to the present embodiment, since the outflow ceiling surfaceportion 36 b has the outflow step surface 41 b, the foreign matter thathas entered from the inflow port 33 a and passed through the flowchannel boundary portion 34 hardly enters the measurement flow channel32. For example, as indicated by a dashed line in FIG. 3, when a largeforeign matter F2 entering from the inflow port 33 a travels linearly inthe depth direction Z and collides with the outflow step surface 41 b ofthe outflow ceiling surface portion 36 b, the possibility that the largeforeign matter F2 returns to the inflow port 33 a so as to follow itsown trajectory is high. As described above, the large foreign matter F2collides with the outflow step surface 41 b of the outflow ceilingsurface portion 36 b in the passage flow channel 31, and thus passesthrough the measurement flow channel 32 which has passed once in theopposite direction, but easily travels toward the upstream side at anangle which makes it difficult to enter the measurement flow channel 32.

On the contrary, unlike the present embodiment, for example, in aconfiguration in which the outflow ceiling surface portion 36 b does nothave the outflow step surface 41 b as shown in FIG. 4, the outflowceiling surface portion 36 b is not orthogonal to the depth direction Z.For that reason, it is conceivable that the large foreign matter F2collides with the outflow ceiling surface portion 36 b which is inclinedas a whole, and enters the measurement flow channel 32 by changing thetraveling direction. Specifically, there is a concern that depending onthe angle at which the large foreign matter F2 rebounds at the outflowceiling surface portion 36 b, as indicated by a dashed line in FIG. 4,the large foreign matter F2 is advanced upstream while rebounding at thebottom surface 37 following the outflow ceiling portion 36 b, therebymaking it easier to enter the measurement flow channel 32. As describedabove, when the traveling direction of the large foreign matter F2changes in the height direction Y with the rebound at the outflowceiling surface portion 36 b, the possibility that the large foreignmatter F2 flows into the measurement flow channel 32 is likely toincrease. In that regard, in the present embodiment, since aconfiguration is realized in which the traveling direction of the largeforeign matter F2 rebounded by the outflow step surface 41 b of theoutflow ceiling surface portion 36 b is less likely to change in theheight direction Y, the large foreign matter F2 can be inhibited frombeing likely to flow into the measurement flow channel 32.

As described above, there is a concern that the detection accuracy ofthe flow rate detection unit 22 is lowered if the flow velocity of theintake air flowing through the measurement flow channel 32 is too smallin the air flow meter 10. On the contrary, according to the presentembodiment, the cross-sectional area of the passage flow channel 31 isreduced by the outflow step surface 41 b on the downstream side of theflow channel boundary portion 34, thereby narrowing the passage flowchannel 31. In that case, the pressure of the intake air in the passageflow channel 31 becomes moderately high, so that the intake air islikely to flow into the measurement flow channel 32, and the flow rateof the intake air in the measurement flow channel 32 becomes moderatelylarge. For that reason, the deterioration of the detection accuracy ofthe flow rate detection unit 22 can be inhibited by the outflow stepsurface 41 b.

According to the present embodiment, since the multiple outflow stepsurfaces 41 b are included in the outflow ceiling surface portion 36 b,the degree of throttling of the passage flow channel 31 can graduallyincrease toward the outflow port 33 b on the downstream side of the flowchannel boundary portion 34. In that case, as compared with theconfiguration in which the degree of throttling of the passage flowchannel 31 increases rapidly toward the outflow port 33 b, the flow ofintake air is less likely to be disturbed due to generation of a vortexor the like. For that reason, the foreign matter caught in the flowdisturbance can be inhibited from entering the measurement flow channel32.

According to the present embodiment, the height dimension Hb is smalleras the outflow step surface 41 b is closer to the outflow port 33 b. Forthat reason, a region around the flow channel boundary portion 34 in thepassage flow channel 31 can be set to be as large as possible in theheight direction Y. This makes it possible to realize a configuration inwhich the passage flow channel 31 is gradually narrowed by the outflowstep surface 41 b toward the outflow port 33 b while creating asituation in which the intake air easily flows into the measurement flowchannel 32 from the passage 31.

According to the present embodiment, the outflow connection surface 42 bextends in parallel with the depth direction Z. For that reason, theoutflow connection surface 42 b can be inhibited from becoming anobstacle to the foreign matter when the foreign matter that has passedthrough the flow channel boundary portion 34 and has traveled linearlyin the depth direction Z toward the outflow port 33 b reaches theoutflow step surface 41 b.

According to the present embodiment, since the outflow step surface 41 bextends in parallel with the height direction Y, the outflow stepsurface 41 b is orthogonal to the depth direction Z which is likely tobe the traveling direction of the intake air from the inflow port 33 a.This makes it possible to inhibit that the foreign matter, whichcollides with the outflow step surface 41 b and rebounds, flows back tothe upstream side in the direction inclined with respect to the heightdirection Y, collides with the bottom surface 37, and rebounds to enterthe measurement flow channel 32.

The first embodiment can be applied to various embodiments andcombinations without departing from the spirit of the presentdisclosure.

As a modification A1, in the inflow step surface 41 a, only one of theupstream end portion and the downstream end portion may be curved inaccordance with the shape of the inflow port 33 a, or both may not becurved. The inflow ceiling surface portion 36 a may or may not be curvedregardless of the shape of the inflow port 33 a. For example, when theinflow port 33 a has a rectangular shape, the inflow step surface 41 aand the inflow connection surface 42 a may be curved.

In a modification A2, the outflow port 33 b may not be formed in arectangular shape. In that case, the outflow step surface 41 b and theoutflow connection surface 42 b may be curved outward or inward inaccordance with the shape of the outflow port 33 b.

Second Embodiment

In an air flow meter 10 of the first embodiment, the passage flowchannel 31 and the measurement flow channel 32 do not overlap with eachother in the width direction X, but in an air flow meter of a secondembodiment, a passage flow channel and a measurement flow channeloverlap with each other in the width direction X. In the secondembodiment, differences from the first embodiment will be mainlydescribed.

An air flow meter 50 illustrated in FIGS. 5 to 8 is a physical quantitydetection device that detects a physical quantity of an intake air in anintake passage 12 in a state of being attached to an intake pipe 12 b,as with the air flow meter 10 of the first embodiment. The air flowmeter 50 includes a housing 51 and a flow rate detection unit 52, andthe housing 51 includes a flow channel forming portion 54, an O-ring 56,a flange portion 57, a flange surface 57 a, and a connector portion 58.Those members and parts correspond to members and parts having the samenames as those of the first embodiment.

The O-ring 56 of the present embodiment does not enter an innerperipheral side of a flange portion 12 c, but is sandwiched between atip portion of the flange portion 12 c and the flange portion 57. Inthat case, the flange surface 57 a faces the tip end face of the flangeportion 12 c through the O-ring 56.

In the housing 51, a flow channel forming portion 54 is provided by ahousing main body 51 a, a front cover 51 b, and a back cover 51 c. Thehousing main body 51 a extends from the flange portion 57 in the heightdirection Y, and the front cover 51 b and the back cover 51 c areattached to the housing main body 51 a in a state in which the frontcover 51 b and the back cover 51 c oppose each other in parallel witheach other across the housing main body 51 a in the width direction X.Both the housing main body 51 a and the flange portion 57 are integrallyformed by molding a synthetic resin material or the like. The frontcover 51 b and the back cover 51 c are also made of a synthetic resinmaterial.

The flow channel forming portion 54 has a passage flow channel 61 and ameasurement flow channel 62, and the passage flow channel 61 has aninflow port 63 a, an outflow port 63 b, a measurement outlet 63 c, aflow channel boundary portion 64, an upstream boundary portion 64 a, anda downstream boundary portion 64 b. An inner peripheral surface 61 a ofthe passage flow channel 61 has a passage ceiling surface 66, an inflowceiling surface portion 66 a, an outflow ceiling surface portion 66 b, apassage bottom surface 67, a passage wall surface 68, an inflow stepsurface 71 a, and an inflow connection surface 72 a. Those members andparts correspond to members and parts having the same names as those ofthe first embodiment. In the present embodiment, the passage bottomsurface 67 extends in parallel with the depth direction Z.

In the present embodiment, unlike the first embodiment, the innerperipheral surface 61 a of the passage flow channel 61 does not have anoutflow step surface and an outflow connection surface. The inflow port63 a is formed in a rectangular shape, and the inflow ceiling surfaceportion 66 a is not curved. For that reason, both a tip portion and abase end portion of the inflow step surface 71 a linearly extend in thewidth direction X. The inflow connection surface 72 a also extendslinearly in the width direction X.

In the present embodiment, unlike the first embodiment, the flow channelboundary portion 34 extends parallel to the depth direction Z. Even inthat case, since the upstream end portion of the measurement flowchannel 62 is not opened toward the side of the inflow port 63 a, evenif the foreign matter traveling linearly in the depth direction Z entersfrom the inflow port 63 a, the foreign matter does not easily enter themeasurement flow channel 62 as it is.

In the inflow ceiling surface portion 66 a, unlike the first embodiment,the step is neither large nor small toward the downstream side, as shownin FIG. 9. Specifically, a depth interval Da and a height dimension Haof each step have the same value. In that case, the entire angle ofinclination in the inflow ceiling surface portion 66 a is the same in aportion closer to the inflow port 63 a and a portion closer to the flowchannel boundary portion 64.

Returning to the description of FIGS. 5 to 7, the flow channel formingportion 54 has a sub-flow channel 75 in addition to the passage flowchannel 61 and the measurement flow channel 62. The sub-flow channel 75is provided between the flange portion 57 and the measurement flowchannel 62 in the height direction Y, and extends in the depth directionZ. When an upstream end portion of the sub-flow channel 75 is referredto as a sub-inlet 75 a and a downstream end portion of the sub-flowchannel 75 is referred to as a sub-outlet 75 b, the sub-inlet 75 a isdisposed between the flange portion 57 and the inflow port 33 a in theheight direction Y, and the sub-outlet 75 b is disposed between theflange portion 57 and the outflow port 63 b. The air flow meter 50includes a pressure detection unit 76, a humidity detection unit 77, anda temperature detection unit 78 in addition to the flow rate detectionunit 52, and the pressure detection unit 76 and the humidity detectionunit 77 detect a pressure and a humidity of the intake air in thesub-flow channel 75.

In the housing main body 51 a, a circuit board 81 is integrally providedby insert molding when the housing main body 51 a is molded. The circuitboard 81 is provided with at least one detection element for detecting aphysical quantity of the intake air flowing through the intake passage12, and a circuit unit for processing a signal detected by the detectionelement. The detection element is provided at a position of the frontsurface or the back surface of the circuit board 81 which is exposed tothe intake air, that is, at a portion which is exposed to the intake airin the intake passage 12, the measurement flow channel 62, and thesub-flow channel 75 and comes into contact with the intake air. Theelectrical connection portion between the circuit board 81 and thedetection element is sealed with a synthetic resin material. The circuitunit is disposed in a circuit chamber Rc sealed by the front cover 51 b.

The housing main body 51 a is provided with a groove opened toward oneside or the other side in the width direction X, and a hole penetratingthrough the housing main body 51 a in the width direction X. The grooveand the hole are covered with the front cover 51 b and the back cover 51c, to thereby provide the passage flow channel 61, the measurement flowchannel 62, and the sub-flow channel 75. A sensor chamber Rs is providedat an intermediate position of the sub-flow channel 75, and the sensorchamber Rs is provided with a pressure detection unit 76 and a humiditydetection unit 77 as detection elements provided on the back surface ofthe circuit board 81. The pressure detection unit 76 and the humiditydetection unit 77 can detect a pressure and a humidity of the intake airflowing through the sub-flow channel 75, respectively.

The circuit board 81 is provided at an intermediate position of thehousing main body 51 a in the width direction X in a state orthogonal tothe width direction X, thereby partitioning the circuit chamber Rc andthe sensor chamber Rs. The circuit chamber Rc is provided between thefront cover 51 b and the circuit board 81, and the sensor chamber Rs isprovided between the back cover 51 c and the circuit board 81. Thecircuit chamber Rc is sealed by attaching the front cover 51 b to thehousing 51, and is completely isolated from an outside.

The flow channel forming portion 54 has a partition wall 84 thatseparates the measurement flow channel 62 and the sub-flow channel 75from each other in the height direction Y. The circuit board 81penetrates the partition wall 84 in the height direction Y and protrudesinto the measurement flow channel 62, and the flow rate detection unit52 is provided in a measurement board portion 81 a which is a protrudingportion.

In a state in which the air flow meter 50 is attached to the intake pipe12 a, an intermediate position between the inflow port 63 a and thesub-inlet port 75 a in the height direction Y is disposed at a positionoverlapping with or close to a center line of the intake pipe 12 a. Inthe above configuration, a gas at a portion close to an inner wallsurface of the intake passage 12 but at a portion close to the centeraway from the inner wall is likely to flow into the passage flow channel61 or the sub-flow channel 75. In that case, the air flow meter 50 canmeasure the physical quantity of the gas in a portion away from theinner wall surface of the intake passage 12, and can reduce ameasurement error of the physical quantity related to a heat and a flowrate decrease in the vicinity of the inner wall surface.

The flow channel forming portion 54 has an inflow restriction portion 85that restricts the inflow of the intake air from the inflow port 63 a.The inflow restriction portion 85 is a projection portion protrudingfrom the passage bottom surface 67 of the passage flow channel 61 towardthe passage ceiling surface 66. The inflow restriction portion 85 has adownstream side surface 85 a facing the downstream side and an uppersurface 85 b facing the passage ceiling surface 66 (hereinafter, alsoreferred to as a ceiling side) and the downstream side surface 85 a andthe upper surface 85 b are included in the passage bottom surface 67.The inflow restriction portion 85 is provided in the inflow port 63 a,and the upstream end portion of the upper surface 85 b is included inthe inflow port 63 a. The downstream side surface 85 a extends obliquelyupward toward the upstream side, and the upper surface 85 b extendsparallel to the depth direction Z.

The inflow restriction portion 85 extends over the pair of passage wallsurfaces 68, and the opening area of the inflow port 63 a is reduced byreducing the height dimension of the inflow port 63 a in the heightdirection. The inflow restriction portion 85 is inclined with respect tothe height Y by extending in a direction away from the outflow port 63 btoward the passage ceiling surface 66 rather than extending parallel tothe height direction Y.

In the present embodiment, as described above, the portion closer to theoutflow port 63 b in the passage flow channel 61 and the portion closerto the measurement outlet 63 c in the measurement flow channel 62overlap with each other in the width direction X. In the flow channelforming portion 54, a groove is provided in the housing main body 51 a,so that the passage flow channel 61 is provided between the housing mainbody 51 a and the back cover 51 c. The measurement flow channel 62 hasan upstream measurement path 91, an intermediate measurement path 92,and a downstream measurement path 93. The upstream measurement path 91extends from the flow channel boundary portion 64 to the downstream sideof the measurement flow channel 62 and is provided between the housingmain body 51 a and the back cover 51 c as well as the passage flowchannel 61. The downstream measurement path 93 extends from themeasurement outlet 63 c to the upstream side of the measurement flowchannel 62, and is provided between the housing main body 51 a and thefront cover 51 b. The downstream measurement path 93 is disposed on theopposite side of the upstream measurement path 91 and the passage flowchannel 61 across the housing main body 51 a in the width direction X.

The intermediate measurement path 92 is a portion connecting theupstream measurement path 91 and the downstream measurement path 93 inthe measurement flow channel 62, and is disposed in a portion where ahole is provided in the housing main body 51 a, so that the intermediatemeasurement path 92 is provided between the front cover 51 b and theback cover 51 c through the hole. The intermediate measurement path 92extends in the depth direction Z, and the intake air flows in theintermediate measurement path 92 in the opposite direction to the intakepassage 12. The intermediate measurement path 92 is divided from thesub-flow channel 75 by the partition wall 84, and the measurement boardportion 81 a of the circuit board 81 is disposed in the intermediatemeasurement path 92. For that reason, the flow rate detection unit 52provided in the intermediate measurement path 92 detects the flow rateof the intake air flowing through the intermediate measurement path 92.

In the width direction X, a width dimension of the intermediatemeasurement path 92 is larger than the width dimensions of the upstreammeasurement path 91 and the downstream measurement path 93. The upstreammeasurement path 91 has a width increasing portion 91 a whose widthdimension gradually increases toward the intermediate measurement path92, and the downstream measurement path 93 has a width decreasingportion 93 a whose width dimension gradually decreases away from theintermediate measurement path 92. The housing main body 51 a has a widthincreasing surface 94 forming the width increasing portion 91 a and awidth decreasing surface 95 forming the width decreasing portion 93 a.The width increasing surface 94 is included in a surface of the housingmain body 51 a facing the back cover 51 c, is not orthogonal to thewidth direction X, and is inclined with respect to the width direction Xby facing the intermediate measurement path 92. The width decreasingsurface 95 is included in a surface of the housing main body 51 a facingthe front cover 51 b, and is inclined with respect to the widthdirection X by facing the intermediate measurement path 92, similarly tothe width increasing surface 94.

The flow rate detection unit 52 is disposed on a surface of themeasurement board portion 81 a facing the front cover 51 b. In theintermediate measurement path 92, the flow rate detection unit 52 isdisposed on the downstream side of the width increasing surface 94. Inthat case, since the flow rate detection unit 52 is hidden behind thewidth increasing surface 94, even if the foreign matter enters themeasurement flow channel 62 from the passage flow channel 61, the widthincreasing surface 94 becomes an obstacle and the foreign matter is lesslikely to reach the flow rate detection unit 52.

According to the present embodiment described so far, similarly to thefirst embodiment, since the inflow ceiling surface portion 66 a has theinflow step surface 71 a, the foreign matter that has entered from theinflow port 63 a is less likely to enter the measurement flow channel62. The inflow step surface 71 a is orthogonal to the depth direction Z.For that reason, similarly to FIG. 3, when the large foreign matter F1entering from the inflow port 63 a moves linearly in the depth directionZ and collides with the inflow step surface 71 a as shown in FIG. 8, itis considered that the possibility that the large foreign matter F1returns to the inflow port 63 a so as to follow its own trajectory ishigh. On the other hand, unlike the present embodiment, in theconfiguration in which the inflow ceiling surface portion 66 a does nothave the inflow step surface 71 a as shown in FIG. 10, the inflowceiling surface portion 66 a is not orthogonal to the depth direction Z,similarly to FIG. 4. For that reason, there is a concern that the largeforeign matter F1 collides with the inflow ceiling surface portion 66 awhich is inclined as a whole, and enters the measurement flow channel 62while changing the traveling direction. In that regard, in the presentembodiment, the inflow ceiling surface portion 66 a restricts therebound direction of the large foreign matter F1, thereby being capableof inhibiting the large foreign matter F1 from entering the measurementflow channel 62.

According to the present embodiment, since the inflow restrictionportion 85 is provided on the passage bottom surface 67 on the oppositeside of the inflow step surface 71 a across the inflow port 63 a, aprobability that the foreign matter entering from the inflow port 63 aand traveling linearly collides with the inflow step surface 71 a. Thisis because a region of the inflow port 63 a which does not face theinflow step surface 71 a, that is, a region which is not aligned withthe inflow step surface 71 a in the depth direction Z can be closed bythe inflow step surface 71 a. For that reason, the foreign matter can beinhibited from entering the measurement flow channel 62 withoutcolliding with the inflow step surface 71 a.

The second embodiment can be applied to various embodiments andcombinations without departing from the spirit of the presentdisclosure.

As a modification B1, the inflow step surface 71 a may not be parallelto the depth direction Z. For example, as shown in FIG. 11, the inflowstep surface 71 a extends obliquely upward toward the upstream side. Inthat configuration, the inflow connection surface 72 a is orthogonal tothe inflow step surface 71 a, and the inflow connection surface 72 aextends obliquely downward toward the upstream side. When an anglebetween the inflow step surface 71 a and the depth direction Z isreferred to as a step angle θz, and an angle between the inflowconnection surface 72 a and the height direction Y is referred to as aconnection angle θy, the step angle θz and the connection angle θy arethe same angles. The angles θz and θy are positive and have relativelysmall absolute values of several degrees to several tens of degrees. Forthat reason, for example, even if the large foreign matter F1 travelinglinearly in the depth direction Z collides with the inflow step surface71 a or the inflow connection surface 72 a, the large foreign matter F1tends to return toward the inflow port 63 a in substantially the samedirection as the depth direction Z.

As shown in FIG. 12, the inflow step surface 71 a extends obliquelydownward toward the upstream side. In that configuration, the inflowconnection surface 72 a is orthogonal to the inflow step surface 71 a,and the inflow connection surface 72 a extends obliquely downward towardthe downstream side. In that case, the step angle θz and the connectionangle θy are negative values and have relatively small absolute valuesof several degrees to several tens of degrees. Even in that case, thelarge foreign matter F1 rebounded at the inflow step surface 71 a andthe inflow connection surface 72 a tends to return toward the inflowport 63 a in substantially the same direction as the depth direction Z.

As a modification B2, the inflow step surface 71 a and the inflowconnection surface 72 a may not be orthogonal to each other. Forexample, the angle between the inflow step surface 71 a and the inflowconnection surface 72 a may be smaller than 90 degrees or larger than 90degrees. It is preferable that a difference between the angle and 90degrees is small to the extent that when the large foreign matter F1traveling linearly in the depth direction Z collides with the inflowstep surface 71 a or the inflow connection surface 72 a, the largeforeign matter F1 tends to return toward the inflow port 63 a insubstantially the same direction as the depth direction Z. Preferredvalues include relatively small absolute values, such as a few degreesto several degrees severity.

As a modification B3, the height dimension Ha of the inflow step surface71 a may not be the same in each step of the inflow ceiling surfaceportion 66 a. For example, as shown in FIG. 13, the height dimension Haof the inflow step surface 71 a gradually decreases as a distance fromthe inflow port 63 a increases. In that configuration, the depthinterval Da is the same for each step. The height dimension Ha of theinflow step surface 71 a may gradually increase as the distance from theinflow port 63 a increases.

As a modification B4, in each step of the inflow ceiling surface portion66 a, both the height dimension Ha and the depth interval Da of theinflow step surface 71 a may be different from each other. For example,as shown in FIG. 14, in each step of the inflow ceiling surface portion66 a, both the height dimension Ha and the depth interval Da graduallyincrease as the distance from the inflow port 63 a increases. It shouldbe noted that both the height dimension Ha and the depth interval Da maygradually decrease as the distance from the inflow port 63 a increases.

As a modification B5, similarly to the first embodiment, the air flowmeter 50 of the second embodiment may have an outflow step surface andan outflow connection surface. For example, as shown in FIG. 15, in theinner peripheral surface 61 a of the passage flow channel 61, an outflowceiling surface portion 66 b of the passage ceiling surface 66 has anoutflow step surface 71 b and an outflow connection surface 72 b. Whilethe outflow step surface 71 b and the outflow connection surface 72 bcorrespond to the same named parts of the first embodiment, in thisconfiguration, the inflow ceiling surface portion 66 a does not have theinflow step surface 71 a and the inflow connection surface 72 a.Similarly, in the above configuration, the outflow step surface 71 b isorthogonal to the depth direction. For that reason, similarly to FIG. 3,when the large foreign matter F2 entering from the inflow port 63 atravels linearly in the depth direction Z and collides with the outflowstep surface 71 b as shown in FIG. 15, it is considered highly likelythat the large foreign matter F2 returns to the inflow port 63 a so asto follow its own trajectory.

On the other hand, unlike the present embodiment, in the configurationin which the outflow ceiling surface portion 66 b does not have theoutflow step surface 71 b as illustrated in FIG. 16, the outflow ceilingsurface portion 66 b does not have a portion perpendicular to the depthdirection as illustrated in FIG. 4. For that reason, there is a concernthat the large foreign matter F2 collides with the outflow ceilingsurface portion 66 b which is inclined as a whole, and enters themeasurement flow channel 62 by changing the traveling direction. In thatregard, according to the present embodiment, the outflow ceiling surfaceportion 66 b restricts the rebound direction of the large foreign matterF2, thereby being capable of inhibiting the large foreign matter F2 fromentering the measurement flow channel 62.

The modification B1 may be applied to the modification B4, and theoutflow step surface 71 b may not be parallel to the depth direction Zb.For example, the outflow step surface 71 b extends obliquely upward orobliquely downward toward the upstream side. In addition, themodification B2 may be applied to the modification B4, and the outflowstep surface 71 b and the outflow connection surface 72 b may not beorthogonal to each other.

As a modification B6, in the modification B5, as shown in FIG. 17, thepassage ceiling surface 66 may have the inflow step surface 71 a and theinflow connection surface 72 a in addition to the outflow step surface71 b and the outflow connection surface 72 b. In the aboveconfiguration, similarly to the first embodiment, both of the largeforeign matter F1 colliding with the inflow ceiling surface portion 66 aand the large foreign matter F2 colliding with the outflow ceilingsurface portion 66 b can exert a deterrent force against entering themeasurement flow channel 62.

As a modification B7, a step may not be formed on the entire inflowceiling surface portion 66 a. For example, as shown in FIG. 18, theinflow ceiling surface portion 66 a has an inflow non-step surface 73 ain addition to the inflow step surface 71 a and the inflow connectionsurface 72 a. The inflow non-step surface 73 a extends obliquelydownward from the downstream end portion of the inflow step surface 71 adisposed at the most downstream side toward the downstream side, and thedownstream end portion of the inflow non-step surface 73 a is disposedat the upstream boundary portion 64 a. Even in the above configuration,a deterrent force against the large foreign matter F1 entering themeasurement flow channel 62 can be exerted on the inflow step surface 71a. The inflow non-step surface 73 a may be disposed upstream of any ofthe inflow step surfaces 71 a or may be disposed between the multipleinflow step surfaces 71 a. The inflow non-step surface 73 a may extendobliquely upward toward the downstream side, or may extend parallel tothe depth direction Z.

The modification B7 is applied to the modification B4, and the step maynot be formed on the entire outflow ceiling surface portion 66 b. Forexample, as shown in FIG. 18, the outflow ceiling surface portion 66 bhas an outflow non-step surface 73 b in addition to the outflow stepsurface 71 b and the outflow connection surface 72 b. The outflownon-step surface 73 b extends obliquely downward from the downstream endportion of the outflow step surface 71 b disposed at the most downstreamside toward the downstream side, and a downstream end portion of theoutflow non-step surface 73 b is disposed at the outflow port 63 b. Evenin the above configuration, the outflow step surface 71 b can exert adeterrent force against the large foreign matter F2 entering themeasurement flow channel 62. The outflow non-step surface 73 b may bedisposed on the upstream side of any of the outflow step surfaces 71 b,or may be disposed between the multiple outflow step surfaces 71 b. Theoutflow non-step surface 73 b may extend obliquely upward toward thedownstream side, or may extend parallel to the depth direction Z.

As a modification B8, the passage bottom surface 67 may be inclined withrespect to the depth direction Z. For example, as shown in FIG. 19, thepassage bottom surface 67 extends obliquely upward toward the upstreamside. In the above configuration, the passage bottom surface 67 inclinedwith respect to the depth direction Z is extended linearly over theinflow port 63 a and the outflow port 63 b. In that case, the flowchannel forming portion 54 does not have the inflow restriction portion85. As a modification B9, as shown in FIG. 20, the flow channel formingportion 54 may not have the inflow restriction portion 85. In that case,at least a part of the outflow ceiling surface portion 66 b is nothidden from the upstream side by the inflow restriction portion 85 inthe depth direction Z. For that reason, all the outflow step surfaces 71b are exposed to the upstream side through the inflow port 63 a.

As a modification B10, the passage bottom surface 67 may have steps. Forexample, as shown in FIG. 21, the passage bottom surface 67 has bottomstep surfaces 67 a and bottom connection surfaces 67 b. The multiplebottom step surfaces 67 a are perpendicular to the depth direction Z inthe same manner as the inflow step surfaces 71 a and the outflow stepsurfaces 71 b, and aligned in the depth direction Z at predeterminedintervals. An installation interval of the bottom step surfaces 67 a islarger than the depth interval Da of the inflow step surfaces 71 a andthe depth interval Db of the outflow step surfaces 71 b. Like the inflowconnection surfaces 72 a and the outflow connection surfaces 72 b, thebottom connection surfaces 67 b extend parallel to the depth direction Zand connect the adjacent bottom step surfaces 67 a.

In the configuration in which the passage bottom surface 67 has thebottom step surfaces 67 a and the bottom connection surfaces 67 b, thepassage ceiling surface 66 may not have the inflow step surfaces 71 aand the outflow step surfaces 71 b. In that case, both of the largeforeign matter colliding with the passage bottom surface 67 can exert adeterrent force against entering the measurement flow channel 62 bychanging the traveling direction of the large foreign matter.

As a modification B11, the passage wall surface 68 may have steps. Forexample, as shown in FIG. 22, the passage wall surface 68 has wall stepsurfaces 68 a and wall connection surfaces 68 b. The wall step surfaces68 a are orthogonal to the depth direction Z in the same manner as thebottom step surfaces 67 a of the modification B10 described above andare aligned in the depth direction Z at predetermined intervals. Aninstallation interval of the wall step surfaces 68 a is larger than thedepth interval Da of the inflow step surfaces 71 a and the depthinterval Db of the outflow step surfaces 71 b, and is, for example, thesame as the installation interval of the bottom step surfaces 67 a.Specifically, the wall step surfaces 68 a and the bottom step surfaces67 a are connected to each other. The wall connection surfaces 68 bextend in parallel to the depth direction Z, similarly to the bottomconnection surfaces 67 b of the modification B10, and connect theadjacent wall step surfaces 68 a. The wall step surfaces 68 a and thewall connection surfaces 68 b are formed on at least one of the pair ofpassage wall surfaces 68.

As a modification B12, the depth interval Da of the inflow step surfaces71 a may not be larger than the depth interval Db of the outflow stepsurfaces 71 b. For example, the depth interval Da may be the same as orsmaller than the depth interval Db.

As a modification B13, the inflow step surfaces 71 a may be provided inthe inflow ceiling surface portion 66 a and the outflow ceiling surfaceportion 66 b one by one. The inflow step surfaces 71 a may be providedon only one of the inflow ceiling surface portion 66 a and the outflowceiling surface portion 66 b.

Third Embodiment

An air flow meter 50 according to a third embodiment has a parallelregion extending linearly in parallel with the depth direction Z. In thepresent embodiment, differences from the second embodiment will bemainly described.

As shown in FIG. 23, a passage flow channel 61 has a parallel region101, a ceiling-side region 102, and a hidden region 103. The parallelregion 101 is a region extending linearly in the depth direction Z so asto connect an inflow port 63 a and an outflow port 63 b, and an upstreamend portion of the parallel region 101 is included in the inflow port 63a and a downstream end portion is included in the outflow port 63 b. Theceiling-side region 102 is a region closer to a ceiling than theparallel region 101 in the height direction Y, and extends from theinflow port 63 a toward a downstream side. In that case, an upstream endportion of the ceiling-side region 102 is included in the inflow port 63a. The hidden region 103 is a region located closer to a passage bottomsurface 67 side (hereinafter, also referred to as a bottom side) thanthe parallel region 101 in the height direction Y, and extends from theoutflow port 63 b to the upstream side. In that case, a downstream endportion of the hidden region 103 is included in the outflow port 63 b.All of the regions 101 to 103 are virtual regions, and the passage flowchannel 61 is not actually divided into the regions 101 to 103. In FIGS.23 to 25, the parallel region 101 is illustrated by dot hatching.

As shown in FIGS. 23 and 24, the inflow port 63 a has a first entranceregion 63 a 1 included in the parallel region 101 and a second entranceregion 63 a 2 included in the ceiling-side region 102. In the inflowport 63 a, the first entrance region 63 a 1 is disposed on a flange tipside of the second entrance region 63 a 2, and those regions 63 a 1 and63 a 2 are aligned in the height direction Y so as to divide the inflowport 63 a into two. The parallel region 101 is a region in which thefirst entrance region 63 a 1 is projected toward the downstream side,and the projection region reaches the outflow port 63 b. On the otherhand, since the ceiling-side region 102 gradually comes closer to thepassage bottom surface 67 as the inflow ceiling surface portion 66 acomes closer to a flow channel boundary portion 64, the ceiling-sideregion 102 is blocked by the inflow ceiling surface portion 66 a fromextending downstream in the depth direction Z. In this case, theceiling-side region 102 is disposed on the upstream side of the inflowceiling surface portion 66 a.

As shown in FIGS. 23 and 25, the outflow port 63 b has a first exitregion 63 b 1 included in the parallel region 101 and a second exitregion 63 b 2 included in the hidden region 103. In the outflow port 63b, the first exit region 63 b 1 is disposed closer to a base end side ofthe flange than the second exit region 63 b 2, and the regions 63 b 1and 63 b 2 are aligned in the height direction Y so as to divide theoutflow port 63 b into two. The parallel region 101 may be referred toas a region in which the first exit region 63 b 1 is projected towardthe upstream side. On the other hand, although the hidden region 103extends upstream along the passage bottom surface 67, the hidden region103 is blocked by the inflow restriction portion 85 from extendingupstream in the depth direction Z due to the protrusion of the inflowrestriction portion 85 from the passage bottom surface 67. In that case,the hidden region 103 is disposed on the downstream side of the inflowrestriction portion 85, and is in a state of being hidden from theupstream side by the inflow restriction portion 85.

As shown in FIG. 23, an inner peripheral surface 61 a of the passageflow channel 61 has a height narrowing surface 105. The height narrowingsurface 105 is included in the passage bottom surface 67 and extendsparallel to the width direction X over a pair of passage wall surfaces68. The height narrowing surface 105 is disposed closer to the outflowport 63 b than the flow channel boundary portion 64 in the depthdirection Z, and extends from the outflow port 63 b toward the upstreamside. The height narrowing surface 105 gradually decreases a heightdimension Hc of the passage flow channel 61 as the height narrowingsurface 105 comes closer to the outflow port 63 b.

The height narrowing surface 105 gradually comes closer to the passageceiling surface 66 as the height narrowing surface 105 comes closer tothe outflow port 63 b, and continuously restricts the passage flowchannel 61. In the width direction X, the width dimension of the passageflow channel 61 is uniform. As the height dimension Hc of the passageflow channel 61 gradually decreases toward the outflow port 63 b, andthe cross-sectional area of the passage flow channel 61 also graduallydecreases. In that case, both the height dimension Hc and thecross-sectional area are smallest at the outflow port 63 b on thedownstream side of the flow channel boundary portion 64 in the passageflow channel 61.

The height dimension of the parallel region 101 remains constant in anypart in the depth direction Z. On the other hand, the height dimensionof the ceiling-side region 102 gradually decreases as the distance fromthe inflow port 63 a increases. In this example, the passage bottomsurface 67 has, in addition to the height narrowing surface 105, aparallel bottom surface portion 106 extending in parallel with the depthdirection Z, and the parallel bottom surface portion 106 extends fromthe upstream end portion of the height narrowing surface 105 toward theupstream side. In that case, the height dimension of the hidden region103 is constant for any portion of the area where the parallel bottomsurface portion 106 is located, but gradually decreases toward theoutflow port 63 b as the area where the height narrowing surface 105 islocated. In the inflow port 63 a, the height dimension of the parallelregion 101 is smaller than the height dimension of the ceiling-sideregion 102. In other words, the height dimension of the first entranceregion 63 a 1 is smaller than the height dimension of the secondentrance region 63 a 2. In that case, the second entrance region 63 a 2and the ceiling-side region 102 inhibits the insufficiency of the inflowamount of the intake air into the passage flow channel 61 while securingthe parallel region 101. In the outflow port 63 b, the height dimensionof the parallel region 101 is smaller than the height dimension of thehidden region 103. In other words, the height dimension of the firstexit region 63 b 1 is larger than the height dimension of the secondexit region 63 b 2. In that case, since the parallel region 101 issecured as large as possible at the outflow port 63 b, the foreignmatter traveling linearly through the parallel region 101 is easilydischarged from the outflow port 63 b as it is.

The height narrowing surface 105 is disposed on the downstream side ofthe inflow restriction portion 85 in the depth direction Z, and ishidden from the upstream side by the inflow restriction portion 85. Forthat reason, in the depth direction Z, the height narrowing surface 105is not exposed to the upstream side from the inflow port 63 a due to thepresence of the inflow restriction portion 85. For example, when aperson looks into the passage flow channel 61 through the inflow port 63a in the depth direction Z, the height narrowing surface 105 cannot bevisually recognized because the sight line is blocked by the inflowrestriction portion 85. However, in a direction angled with respect tothe depth direction Z, the height narrowing surface 105 may be exposedfrom the inflow port 63 a, and a person looking into the depth side ofthe inflow restriction portion 85 can visually recognize the heightnarrowing surface 105 from that direction.

For example, when a large foreign matter F3 traveling linearly in thedepth direction Z enters the passage flow channel 61 from the firstentrance region 63 a 1 of the inflow port 63 a, the large foreign matterF3 simply travels linearly in the parallel region 101 and exits from thefirst exit region 63 b 1 of the outflow port 63 b. For that reason, evenif the passage flow channel 61 is narrowed by the height narrowingsurface 105, the large foreign matter F3 traveling linearly in the depthdirection Z that travels linearly in the parallel region 101 does noteasily collide with the height narrowing surface 105 or enter themeasurement flow channel 62.

On the other hand, unlike the present embodiment, in the configurationin which the height narrowing surface 105 is exposed to the upstreamside from the inflow port 63 a in the depth direction Z, there is aconcern that foreign matter will collide with the height narrowingsurface 105 and rebounds, thereby easily entering the measurement flowchannel 32. For example, as shown in FIG. 26, in the configuration inwhich the height narrowing surface 105 is exposed to the upstream sidefrom the inflow port 63 a in the depth direction Z with no provision ofthe inflow restriction portion 85, it is assumed that a large foreignmatter F4 traveling linearly in the depth direction Z collides with theheight narrowing surface 105. In that case, depending on the angle atwhich the large foreign matter F4 rebounds at the height narrowingsurface 105, the large foreign matter F4 may easily enter themeasurement flow channel 62 while the large foreign matter F4 reboundsat the outflow ceiling surface portion 66 b following the heightnarrowing surface 105 and advances toward the upstream side. Asdescribed above, when the traveling direction of the large foreignmatter F4 rebounded at the height narrowing surface 105 changes withrespect to the height direction Y, the possibility that the largeforeign matter F4 enters the measurement flow channel 62 is likely to beincreased. In that regard, in the present embodiment, since the largeforeign matter F4 that has traveled linearly in the depth direction Z isconfigured to hardly collide with the height narrowing surface 105, thelarge foreign matter F4 is inhibited from entering the measurement flowchannel 62.

In the present embodiment, the outflow ceiling surface portion 66 b andthe flow channel boundary portion 64 extend parallel to the depthdirection Z, and the upstream end portion of the measurement flowchannel 62 is opened to the flange tip side in the height direction Y.In that case, the upstream end portion of the measurement flow channel62 is not opened toward either the inflow port 63 a or the outflow port63 b. The parallel region 101 extends in parallel with the flow channelboundary portion 64, and the outflow ceiling surface portion 66 b andthe flow channel boundary portion 64 define a ceiling-side range of theparallel region 101. Because the flow channel boundary portion 64extends in parallel with the depth direction Z, the flow channelboundary portion 64 is not exposed to the upstream side from the inflowport 63 a. For that reason, for example, the large foreign matter F3traveling linearly in the depth direction Z in the parallel region 101does not easily enter the measurement flow channel 62 without changingthe traveling direction. The parallel region 101 extends in parallelwith the upper surface 85 b of the inflow restriction portion 85, andthe upper surface 85 b defines a bottom side range of the parallelregion 101.

According to the present embodiment described so far, since the heightnarrowing surface 105 is not exposed to the upstream side from theinflow port 63 a in the depth direction Z while reserving the parallelregion 101 in the passage flow channel 61, a configuration in which theforeign matter is less likely to collide with the height narrowingsurface 105 can be realized. This makes it possible to inhibit that theforeign matter entering the passage flow channel 61 through the inflowport 63 a and traveling linearly collides with the height narrowingsurface 105 and rebounds to return to the upstream side and enter themeasurement flow channel 62, despite passing through the flow channelboundary portion 64.

In the passage flow channel 61, the parallel region 101 is reserved as aprojection region of the first entrance region 63 a 1 of the inflow port63 a. For that reason, the foreign matter that travels linearly in thedepth direction Z in the parallel region 101 tends to exit from theoutflow port 63 b without colliding with any portion of the innerperipheral surface 61 a of the passage flow channel 61. As describedabove, for example, as compared with the configuration in which theregion extending linearly in the depth direction Z is not secured in thepassage flow channel 61, the possibility that the foreign mattercollides with the inner peripheral surface 61 a of the passage flowchannel 61 is reduced, thereby being capable of reducing the entry ofthe foreign matter into the measurement flow channel 62.

In addition, since the height narrowing surface 105 reduces the passageflow channel 61 on the downstream side of the flow channel boundaryportion 64, the amount of intake air flowing from the passage flowchannel 61 into the measurement flow channel 62 is likely to increase.In this example, because the flow rate detection unit 52 is a thermaltype flow rate sensor, it is preferable that a flow rate of the intakeair in the measurement flow channel 62 is high to some extent in orderto properly maintain the detection accuracy of the flow rate detectionunit 52. In other words, it is preferable that the flow rate of theintake air from the passage flow channel 61 to the measurement flowchannel 62 is somewhat high. The inflow amount into the measurement flowchannel 62 increases or decreases in accordance with a relationshipbetween the cross-sectional area and the flow channel length of thepassage flow channel 61 and the measurement flow channel 62, and it isconceivable that the inflow amount increases as a minimumcross-sectional area in the passage flow channel 61 decreases. On theother hand, according to the present embodiment, since the minimumcross-sectional area of the passage flow channel 61 is reduced by theamount corresponding to the provision of the height narrowing surface105, the inflow amount into the measurement flow channel 62 is increasedas compared with the configuration in which the height narrowing surface105 is not provided. This makes it possible to optimize the detectionaccuracy of the flow rate detection unit 52 in the measurement flowchannel 62.

According to the present embodiment, since the flow channel boundaryportion 64 is not exposed to the upstream side from the inflow port 63 ain the depth direction Z, the foreign matter entering from the inflowport 63 a can be inhibited from directly entering the measurement flowchannel 62 without colliding with the inner peripheral surface 61 a ofthe passage flow channel 61. This makes it possible to exert a deterrentforce against lowering of the detection accuracy of the flow ratedetection unit 52 due to the foreign matter adhering to the flow ratedetection unit 52 or the like.

According to the present embodiment, since the height narrowing surface105 is an inclined surface, the height dimension Hc and thecross-sectional area of the passage flow channel 61 are graduallyreduced. For that reason, as compared with a configuration in which theheight dimension Hc and the cross-sectional area of the passage flowchannel 61 are rapidly reduced, for example, turbulence of an air flowis less likely to occur in the periphery of the height narrowing surface105. In that case, since the turbulence is less likely to occur also inthe intake air flowing into the measurement flow channel 62, thedetection accuracy of the flow rate detection unit 52 can be inhibitedfrom being lowered due to the turbulence in the air flow generated inthe measurement flow channel 62.

According to the present embodiment, the passage bottom surface 67 hasthe parallel bottom surface portion 106 extending parallel to theparallel region 101. In that case, for example, the flow of the intakeair in the parallel region 101 is less likely to be disturbed ascompared with a configuration in which the passage bottom surface 67does not have a portion extending in parallel with the parallel region101. For that reason, the parallel bottom surface portion 106 can urgethe foreign matter that travels linearly in the depth direction Z in theparallel region 101 to exit from the outflow port 63 b as it is.

According to the present embodiment, since the inflow restrictionportion 85 is simply provided so as to cover and hide the heightnarrowing surface 105 from the upstream side, the foreign mattertraveling linearly in the depth direction Z is less likely to collidewith the height narrowing surface 105. For example, unlike the presentembodiment, when the height narrowing surface 105 is hidden on thedownstream side of the inflow ceiling surface portion 66 a, there is aconcern that a large number of considerations such as the position ofthe flow channel boundary portion 64 and the branching angle of themeasurement flow channel 62 with respect to the passage flow channel 61occur in the stage of design change. On the other hand, in the method ofproviding the inflow restriction portion 85, although there is a need tooptimize the inflow amount from the inflow port 63 a at the stage ofdesign change, it is considered that a design load is relatively easilyreduced.

According to the present embodiment, the whole of the outflow port 63 bis not included in the parallel region 101, but the first exit region 63b 1 of the outflow port 63 b is included in the parallel region 101,while the second exit region 63 b 2 is not included in the parallelregion 101. For that reason, for example, when the turbulence of the airflow occurs in the passage flow channel 61, the possibility that theturbulence is included not in the parallel region 101 but in the hiddenregion 103, for example, can be ensured. In other words, the possibilitythat the turbulence or the like of the air flow is discharged to theoutside from the second exit region 63 b 2 instead of the first exitregion 63 b 1. This makes it possible to inhibit a state in which theforeign matter does not easily travel linearly in the depth direction Zin the parallel region 101 due to the turbulence of the air flow or thelike.

The third embodiment can be applied to various embodiments andcombinations without departing from the spirit of the presentdisclosure.

As a modification C1, the inflow ceiling surface portion 66 a may havesteps. For example, the second embodiment is applied, and as shown inFIG. 27, the inflow ceiling surface portion 66 a has an inflow stepsurface 71 a and an inflow connection surface 72 a. Also in the aboveconfiguration, the ceiling-side region 102 is formed between the inflowceiling surface portion 66 a and the parallel region 101. In the aboveconfiguration, when a foreign matter traveling linearly in the depthdirection Z enters the ceiling-side region 102, the foreign mattercollides with the inflow step surface 71 a and rebounds to the inflowport 63 a side, thereby inhibiting the entry of the foreign matter intothe measurement flow channel 62.

As a modification example C2, the height narrowing surface 105 may havesteps. For example, the modification B10 is applied, and as shown inFIG. 28, the height narrowing surface 105 has bottom step surfaces 67 aand bottom connection surfaces 67 b. The height narrowing surface 105with the above configuration does not continuously narrows the passageflow channel 61 while coming closer to the outflow port 63 b, butnarrows the passage flow channel 61 in a stepwise manner. In the aboveconfiguration, the height dimension Hc and the cross-sectional area ofthe passage flow channel 61 are gradually reduced toward the outflowport 63 b. In this example, a downstream end portion of the bottomconnection surface 67 b disposed on the most downstream side is includedin the outflow port 63 b, and the height dimension Hc and thecross-sectional area of the portion formed by the bottom connectionsurface 67 b are the smallest in the passage flow channel 61.

As a modification C3, both the inflow ceiling surface portion 66 a andthe height narrowing surface 105 may have steps by combining themodification C1 and the modification C2 together. For example, as shownin FIG. 29, the inflow ceiling surface portion 66 a has an inflow stepsurface 71 a and an inflow connection surface 72 a, and the heightnarrowing surface 105 has a bottom step surface 67 a and a bottomconnection surface 67 b.

As a modification C4, the inner peripheral surface 61 a of the passageflow channel 61 may have multiple height narrowing surfaces. Forexample, as shown in FIG. 30, the inner peripheral surface 61 a has abottom restriction surface 105 a and a ceiling restriction surface 105 bas height narrowing surfaces. The bottom restriction surface 105 a isthe height narrowing surface 105 of the third embodiment, and isincluded in the passage bottom surface 67. The ceiling restrictionsurface 105 b is included in the outflow ceiling surface portion 66 b,and extends over the pair of passage wall surfaces 68 in the same manneras the bottom restriction surface 105 a. A downstream end portion of theceiling restriction surface 105 b is included in the outflow port 63 b,and the ceiling restriction surface 105 b gradually comes closer to thepassage bottom surface 67 as the ceiling restriction surface 105 b comescloser to the outflow port 63 b in the height direction Y. In addition,almost the whole of the outflow ceiling surface portion 66 b is theceiling restriction surface 105 b. In the above configuration, sinceboth the bottom restriction surface 105 a and the ceiling restrictionsurface 105 b narrow the passage flow channel 61, the degree ofnarrowing the passage flow channel 61 can be set to be as large aspossible.

As a modification C5, the passage flow channel 61 may have a pluralityof hidden regions. For example, as shown in FIG. 30 and FIG. 31, thepassage flow channel 61 is configured to have a bottom hidden region 103a and a ceiling hidden region 103 b as hiding regions. The bottom hiddenregion 103 a is the hidden region 103 of the third embodiment, and isformed between the parallel region 101 and the passage bottom surface67. The ceiling hidden region 103 b is a region formed between theparallel region 101 and the outflow ceiling surface portion 66 b.

For example, as shown in FIG. 31, the ceiling hidden region 103 b mayextend from the outflow port 63 b toward the downstream side. In theabove configuration, the outflow port 63 b has multiple second exitregions 63 b 2, the bottom hidden region 103 a extends from the secondexit regions 63 b 2 on the bottom side, and the ceiling hidden region103 b extends from the second exit regions 63 b 2 on the ceiling-sidetoward the upstream side. The ceiling hidden region 103 b is disposed onthe downstream side of the inflow ceiling surface portion 66 a in thedepth direction Z, and is in a state of being hidden from the upstreamside by the inflow ceiling surface portion 66 a.

The ceiling hidden region 103 b may be formed independently of theoutflow port 63 b, as shown in FIG. 31, for example. In the aboveconfiguration, as compared with the third embodiment, the downstreamboundary portion 64 b of the flow channel boundary portion 64 isdisposed at a position away from the passage bottom surface 67. In thatcase, the flow channel boundary portion 64 does not extend in parallelto the depth direction Z, but extends obliquely to the bottom sidetoward the downstream side, thereby being inclined with respect to thedepth direction Z. In this example, the upstream end portion of theceiling restriction surface 105 b is included in the outflow port 63 b.As a result, the passage flow channel 61 is shaped such that a portionaround the downstream boundary portion 64 b expands toward a sideopposite to the passage bottom surface 67, and that portion is theceiling hidden region 103 b. The ceiling hidden region 103 b is a regionsurrounded by the ceiling restriction surface 105 b, the flow channelboundary portion 64, and the parallel region 101.

As a modification C6, the inner peripheral surface 61 a of the passageflow channel 61 may have a width narrowing surface that narrows thepassage flow channel 61 in the width direction as a distance from theoutflow port 63 b decreases. Specifically, at least one of the pair ofpassage wall surfaces 68 may include the width narrowing surface. Forexample, as shown in FIG. 32, one of the pair of passage wall surfaces68 includes a width narrowing surface 107. The width narrowing surface107 extends in parallel to the height direction Y in a state where thewidth narrowing surface 107 extends over the outflow ceiling surfaceportion 66 b and the passage bottom surface 67. The width narrowingsurface 107 is disposed closer to the outflow port 63 b than the flowchannel boundary portion 64 in the depth direction Z, and extends fromthe outflow port 63 b toward the upstream side. The width narrowingsurface 107 gradually decreases the width dimension Wa of the passageflow channel 61 as the width narrowing surface 107 comes closer to theoutflow port 63 b. The width narrowing surface 107 comes graduallycloser to the other passage wall surface 68 as the width narrowingsurface 107 comes closer to the outflow port 63 b, and continuouslyreduces the width dimension Wa and the cross-sectional area of thepassage flow channel 61.

The parallel region 101 is a region between the width narrowing surface107 and the passage wall surface 68 without the width narrowing surface107 in the width direction X. The passage flow channel 61 has, inaddition to the parallel region 101, a side region 104 provided on theside of the parallel region 101 in the width direction X. The sideregion 104 is a region extending from the inflow port 63 a toward thedownstream side, and is disposed on the upstream side of the widthnarrowing surface 107. In the above configuration, it is considered thatthe foreign matter that has entered the side region 104 from the inflowport 63 a travels linearly in the depth direction Z to rebound at thewidth narrowing surface 107, but it is considered that the travelingdirection of the foreign matter is likely to change in the widthdirection X in the rebound, but is less likely to change in the heightdirection Y. For that reason, it is difficult for the foreign matter toeasily enter the measurement flow channel 62 due to collision with thewidth narrowing surface 107.

The passage wall surface 68 having the width narrowing surface 107 has aparallel wall surface portion 108 extending parallel to the depthdirection Z. The parallel wall surface portion 108 extends from theupstream end portion of the width narrowing surface 107 toward theupstream side, and the upstream end portion of the parallel wall surfaceportion 108 is included in the inflow port 63 a. As a result, theparallel wall surface portion 108 prompts the foreign matter thattravels linearly in the depth direction Z in the parallel region 101 tomove linearly as it is and exit from the outflow port 63 b.

The width narrowing surface 107 may have steps instead of an inclinedsurface. For example, similarly to the passage ceiling surface 66 of thesecond embodiment, the width narrowing surface 107 has a step surfaceand a connection surface.

As a modification C7, a portion with the lowest height dimension Hc orthe lowest cross-sectional area in the passage flow channel 61 may notbe the outflow port 63 b. For example, the portion may be anintermediate portion between the flow channel boundary portion 64 andthe outflow port 63 b in the depth direction Z. Even in that case, ifthe height narrowing surface 105 is configured to narrow the passageflow channel 61, a flow of the intake air in the measurement flowchannel 62 can be appropriately accelerated.

As a modification C8, at least one of the inflow port 63 a and theoutflow port 63 b may be entirely included in the parallel region 101.For example, the outflow port 63 b is configured to have only the firstoutlet area 63 b 1 of the first exit region 63 b 1 and the second exitregion 63 b 2.

As a modification C9, the downstream boundary portion 64 b of the flowchannel boundary portion 64 may be disposed on the bottom side of theupstream boundary portion 64 a in the height direction Y. For example,the downstream boundary portion 64 b is exposed to the upstream sidefrom the inflow port 63 a in the depth direction Z. Even in thatconfiguration, if the outflow ceiling surface portion 66 b extends inparallel with the depth direction Z, the configuration does notcorrespond to a configuration in which the outflow ceiling surfaceportion 66 b narrows the passage flow channel 61 at a position exposedto the upstream side from the inflow port 63 a in the depth direction Z.

As a modification C10, the passage bottom surface 67 may not have theparallel bottom surface portion 106. For example, it is assumed thatsubstantially the whole of the passage bottom surface 67 is the heightnarrowing surface 105. In that configuration, the height narrowingsurface 105 extends from the base end portion of the inflow restrictionportion 85 toward the downstream side. In that case, the heightnarrowing surface 105 is in a state of being extended over the inflowrestriction portion 85 and the outflow port 63 b.

Fourth Embodiment

In an air flow meter 50 according to a fourth embodiment, a flow channelboundary portion 64 is not exposed to an upstream side through an inflowport 63 a. In the present embodiment, similarly to the third embodiment,differences from the second embodiment will be mainly described.

As shown in FIG. 33, a flow channel forming portion 54 has a flowchannel partition portion 111 that divides the passage path 61 to have ameasurement flow channel 62 separate from a passage flow channel 61. Theflow channel partition portion 111 is provided on the downstream side ofthe flow channel boundary portion 64 in the depth direction Z and on theopposite side of a passage bottom surface 67 across the passage flowchannel 61 in the height direction Y. A partition top portion 111 a,which is an upstream end portion of the flow channel partition portion111, serves as a downstream boundary portion 64 b of the flow channelboundary portion 64. In that case, the partition top portion 111 a islocated at the same position as that of the downstream boundary portion64 b. A height dimension of the flow channel partition portion 111gradually decreases as the flow channel partition portion 111 comescloser to the flow channel boundary portion 64 in the depth direction Z,and the smallest portion of the height dimension is the partition topportion 111 a. In that case, the partition top portion 111 a is a topside extending in the width direction X. It can be conceivable that theflow channel partition portion 111 partitions the passage flow channel61 and the measurement flow channel 62 vertically in the heightdirection Y.

The flow channel partition portion 111 is included in a housing mainbody 51 a of a housing 51. In the flow channel partition portion 111, asurface facing the bottom side forms an outflow ceiling surface portion66 b, and the surface facing the opposite side to the passage bottomsurface 67 forms an inner peripheral surface of the measurement flowchannel 62.

The flow channel forming portion 54 has a ceiling projection portion 112protruding toward the bottom side in addition to the flow channelpartition portion 111. The ceiling projection portion 112 is provided onthe upstream side of the outflow ceiling surface portion 66 b. In theheight direction Y, the ceiling top portion 112 a, which is thebottom-side end portion of the ceiling projection portion 112, forms theupstream boundary portion 64 a of the flow channel boundary portion 64.In that case, it can be conceivable that the ceiling top portion 112 ais located at the same position as that of the upstream boundary portion64 a. A depth dimension of the ceiling projection portion 112 in thedepth direction Z gradually decreases as the ceiling projection portion112 comes closer to the passage bottom surface 67 in the heightdirection Y, and a portion having the smallest depth dimension becomesthe ceiling top portion 112 a. In that case, the ceiling top portion 112a is a top side extending in the width direction X.

The ceiling projection portion 112 is included in the housing main body51 a of the housing 51. In the ceiling projection portion 112, a surfacefacing the upstream side in the depth direction Z forms the inflowceiling surface portion 66 a, and the surface facing the downstream sideforms the inner peripheral surface of the measurement flow channel 62.

In the present embodiment, the partition top portion 111 a is notexposed to the upstream side through the inflow port 63 a. For example,when a person looks into the passage flow channel 61 from the inflowport 63 a, even if the direction of the looking-in is changed, thepartition top portion 111 a cannot be visually recognized. In otherwords, the partition top portion 111 a is hidden from the upstream sideby the inflow restriction portion 85 and the ceiling projection portion112, and the sight line of the person from the inflow port 63 a isblocked by the inflow restriction portion 85 and the ceiling projectionportion 112. The fact that the partition top portion 111 a is notexposed means that the flow channel boundary portion 64 is also notexposed to the upstream side from the inflow port 63 a.

The inflow restriction portion 85 corresponds to a bottom projectionportion protruding from the passage bottom surface 67 toward the ceilingside. The upper surface 85 b of the inflow restriction portion 85 may bereferred to as an upper end portion of the inflow restriction portion85, and if the upstream end portion of the upper surface 85 b isreferred to as a restriction top portion 85 c, the restriction topportion 85 c is also included in the upper end portion of the inflowrestriction portion 85.

In the passage flow channel 61, a virtual line connecting therestriction top portion 85 c of the inflow restriction portion 85 andthe ceiling top portion 112 a of the ceiling projection portion 112 isreferred to as a connecting line PL. The connecting line PL may also bereferred to as a virtual line expressing the sight line that allows aperson to see a portion close to the partition top portion 111 a whenlooking into the passage flow channel 61 from the inflow port 63 a, forexample. In addition, for example, in a configuration in which themultiple ceiling projection portions and the multiple bottom projectionportions are present on the upstream side of the flow channel boundaryportion 64, a virtual line in which a connecting angle θa, which is aninclination angle with respect to the depth direction Z, has a maximumvalue, among the virtual lines connecting the tip portion of eachceiling projection portion and the tip portion of each bottom projectionportion, is referred to as the connecting line PL.

When a virtual line extending in parallel with the depth direction Z isreferred to as a depth reference line Za, the connecting angle θa is anangle of a portion facing toward the downstream side between theconnecting line PL and the depth reference line Za. In that case, theconnecting angle θa is a side in which the side where the downstreamside portion of the connecting line PL is away from the passage bottomsurface 67 increases with a positive value, and a side in which the sidewhere the downstream side portion of the connecting line PL comes closerto the passage bottom surface 67 increases with a negative value. Forthat reason, as shown in FIG. 33, when the connecting line PL isinclined toward the downstream side so as to be away from the passagebottom surface 67, the connecting angle θa has the positive value. Onthe other hand, when the connecting line PL is inclined toward thedownstream side so as to comes closer to the passage bottom surface 67,the connecting angle θa has the negative value.

The inner peripheral surface 61 a of the passage flow channel 61 has aninflow upper end portion 113 and an outflow upper end portion 114. Theinflow upper end portion 113 is an end portion of the inflow port 63 aopposite to the passage bottom surface 67 in the height direction Y, andthe outflow upper end portion 114 is an end portion of the outflow port63 b opposite to the passage bottom surface 67 in the height directionY. The inflow upper end portion 113 is located farther from the passagebottom surface 67 than the ceiling top portion 112 a in the heightdirection Y. The inflow upper end portion 113 is located farther fromthe passage bottom surface 67 than the partition top portion 111 a inthe height direction Y. In this manner, since the inflow upper endportion 113 is disposed at a position spaced apart from the passagebottom surface 67 as far as possible, the open area of the inflow port63 a is set to be as large as possible. For that reason, it is inhibitedthat the amount of intake air flowing in from the inflow port 63 a isinsufficient and the detection accuracy of the flow rate detection unit52 is lowered.

The outflow upper end portion 114 is located at a position closer to thebottom than the ceiling top portion 112 a in the height direction Y. Inthis manner, since the outflow upper end portion 114 is disposed asclose as possible to the passage bottom surface 67, an open area of theoutflow port 63 b is set to be as small as possible. For that reason,since a pressure of the intake air flowing out from the outflow port 63b is increased, the intake air is likely to flow into the measurementflow channel 62, and the amount of the intake air flowing into themeasurement flow channel 62 is insufficient to inhibit the detectionaccuracy of the flow rate detection unit 52 from being lowered. Inaddition, the outflow upper end portion 114 is located farther from thepassage bottom surface 67 than the restriction top portion 85 c in theheight direction Y.

In the height direction Y, the partition top portion 111 a is disposedon the side opposite to the passage bottom surface 67 across theconnecting line PL, so that the partition top portion 111 a is notexposed to the upstream side from the inflow port 63 a. In that case,the connecting line PL passes between the partition top portion 111 aand the passage bottom surface 67, and the ceiling projection portion112 enters between the partition top portion 111 a and the restrictiontop portion 85 c. For that reason, as indicated by a solid line in FIG.34, when a large foreign matter F5 that has entered the passage flowchannel 61 from the inflow port 63 a travels linearly along theconnecting line PL, the large foreign matter F5 passes through thebottom side of the partition top portion 111 a in the height directionY, and is likely to collide with the outflow ceiling surface portion 66b. As a result of that collision, the traveling direction of the largeforeign matter F5 changes with respect to the height direction Y, but islikely to exit from the outflow port 63 b. In other words, the largeforeign matter F5 traveling linearly in the passage flow channel 61 doesnot collide with the inner peripheral surface 61 a of the passage flowchannel 61, and is less likely to enter the measurement flow channel 62as it is.

On the other hand, unlike the present embodiment, in the configurationin which the partition top portion 111 a is exposed to the upstream sidefrom the inflow port 63 a as shown in FIG. 35, when a large foreignmatter F6 travels linearly along the connecting line PL, there is aconcern that the large foreign matter F6 enters the measurement flowchannel 62 as it is. In that case, the large foreign matter F6 does notcollide with the inner peripheral surface 61 a and enters themeasurement flow channel 62 even though the traveling direction is notchanged. In the above configuration, in the height direction Y, theconnecting line PL passes through the side opposite to the passagebottom surface 67 across the partition top portion 111 a, and theupstream end portion of the measurement flow channel 62 and the flowchannel boundary portion 64 are exposed to the upstream side from theinflow port 63 a. In that case, for example, when a person looks intothe passage flow channel 61 from the inflow port 63 a, an innerperipheral surface of the measurement flow channel 62 or the flowchannel boundary portion 64 can be visually recognized.

Returning to the description of FIG. 33, the passage flow channel 61 hasa straight region 115. The straight region 115 is a region linearlyextending so as to connect the inflow port 63 a and the outflow port 63b, and the upstream end portion of the straight region 115 is includedin the inflow port 63 a and the downstream end is included in theoutflow port 63 b. Unlike the parallel region 101 of the thirdembodiment, the straight region 115 is not parallel to the depthdirection Z but inclined with respect to the depth direction Z. In thepresent embodiment, the straight region 115 is inclined with respect tothe depth direction Z so as to come closer to the passage bottom surface67 toward the downstream side. The inclination direction is opposite tothe connecting line PL, and a straight angle θb indicating theinclination angle with respect to the depth direction Z has a negativevalue. The straight angle θb is an angle of a portion open to thedownstream side between the straight region 115 and the reference lineZa. On the other hand, similarly to the parallel region 101 of the thirdembodiment, a height dimension of the straight region 115 is uniform inany part in the depth direction Z.

As shown in FIG. 34, when a large foreign matter F7 flowing in from theinflow port 63 a travels straight along the straight region 115, thelarge foreign matter F7 exits from the outflow port 63 b simply bytraveling linearly along the straight region 115. In this example, asdescribed above, the inclination direction with respect to the depthdirection Z is opposite between the straight region 115 and theconnecting line PL. In that case, if the air flow meter 50 is installedin the intake passage 12 so that the amount of large foreign matter F7traveling linearly along the straight region 115 increases among theforeign matter contained in the intake air, the number of foreign mattersuch as the large foreign matter F5 traveling along the connecting linePL itself is likely to decrease. This makes it easy to exert a deterrentforce against foreign matter entering the passage flow channel 61 fromthe inflow port 63 a entering the measurement flow channel 62 withoutcolliding with the inner peripheral surface 61 a.

According to the present embodiment described so far, since thepartition top portion 111 a is not exposed to the upstream side throughthe inflow port 63 a, the foreign matter such as the large foreignmatter F5 that travels linearly through the passage flow channel 61 doesnot collide with the inner peripheral surface 61 a and enters themeasurement flow channel 62 as it is, which is unlikely to occur. Thismakes it possible to inhibit the foreign matter from adhering to theflow rate detection unit 52 of the measurement flow channel 62, and thedetection accuracy of the flow rate detection unit 52 from being loweredby the foreign matter.

According to the present embodiment, since the partition top portion 111a and the downstream boundary portion 64 b coincide with each other, aconfiguration in which the partition top portion 111 a is not exposed tothe upstream side through the inflow port 63 a is realized, therebybeing capable of realizing a configuration in which the flow channelboundary portion 64 is also not exposed to the upstream side through theinflow port 63 a. For that reason, the foreign matter such as the largeforeign matter F5 traveling linearly through the passage flow channel 61can be surely inhibited from directly entering the measurement flowchannel 62 without colliding with the inner peripheral surface 61 a.

According to the present embodiment, since the connecting line PL passesthrough passage bottom surface 67 side of the partition top portion 111a, a configuration in which the partition top portion 111 a is notexposed to the upstream side through the inflow port 63 a can berealized.

According to the present embodiment, the partition top portion 111 a andthe upstream boundary portion 64 a coincide with each other. In otherwords, the upstream boundary portion 64 a is not disposed on the bottomside of the partition top portion 111 a. For that reason, even thoughthe partition top portion 111 a is not exposed to the upstream sidethrough the inflow port 63 a, the upstream end portion of themeasurement flow channel 62 and the flow channel boundary portion 64 canbe prevented from being exposed to the upstream side from the inflowport 63 a. As a result, the foreign matter such as the large foreignmatter F5 that travels linearly along the connecting line PL can beinhibited from entering the measurement flow channel 62 as it is.

According to the present embodiment, since the ceiling top portion 112 ais disposed at a height position between the partition top portion 111 aand the restriction top portion 85 c in the height direction Y, thestraight region 115 can be secured by the passage flow channel 61. Inthis example, unlike the present embodiment, for example, in aconfiguration in which the ceiling top portion 112 a is disposed at aposition closer to the passage bottom surface 67 than both of thepartition top portion 111 a and the restriction top portion 85 c in theheight direction Y, it is difficult to secure the straight region 115 inthe passage flow channel 61 in an appropriate state. In addition, evenin a configuration in which the ceiling top portion 112 a is disposed ata position farther from the passage bottom surface 67 than both of thepartition top portion 111 a and the restriction top portion 85 c in theheight direction Y, it is similarly difficult to secure the straightregion 115 in an appropriate state in the passage flow channel 61.

On the other hand, according to the present embodiment, a positionalrelationship of the partition top portion 111 a, the restriction topportion 85 c, and the ceiling top portion 112 a is set so that thestraight region 115 can be secured in an appropriate state. For thatreason, the foreign matter such as the large foreign matter F6 travelinglinearly through the passage flow channel 61 can be inhibited fromentering the measurement flow channel 62 as it is, and a configurationin which the foreign matter such as the large foreign matter F7 is urgedto exit from the outflow port 63 b as it is can be realized. Examples ofthe configuration that can secure the straight region 115 in theappropriate state include a configuration in which the inclination angleof the straight region 115 with respect to the depth direction Z doesnot become too large, a configuration in which the cross-sectional areaof the straight region 115 does not become too small, and the like.

According to the present embodiment, since the inflow restrictionportion 85 has a function of defining the angle of the connecting linePL as the bottom projection portion, there is no need to newly install adedicated member or a dedicated portion for defining the angle of theconnecting line PL in the passage flow channel 61. This makes itpossible to inhibit the complexity of the configuration of the air flowmeter 50 and the tendency of disturbance to occur in the flow of theinflow air in the passage flow channel 61 due to the increase in thenumber of dedicated members and dedicated parts.

According to the present embodiment, since the partition top portion 111a is disposed at a position hidden on the depth side of the inflowrestriction portion 85 and the ceiling projection portion 112 in thedepth direction Z, the partition top portion 111 a can be surelyinhibited from being exposed on the upstream side from the inflow port63 a. In that case, a configuration can be realized in which thepartition top portion 111 a is not exposed to the upstream side from theinflow port 63 a by using the shapes of the passage ceiling surface 66and the inflow port 63 a. For that reason, for example, there is no needto newly install a dedicated member or a dedicated portion for coveringthe partition top portion 111 a.

The fourth embodiment can be applied to various embodiments andcombinations without departing from the scope of the present disclosure.

As a modification D1, the bottom projection portion does not have to bethe inflow restriction portion 85. For example, as shown in FIG. 36, thebottom projection portion 117 is provided at a position spaceddownstream from the inflow port 63 a. The bottom projection portion 117is provided on the upstream side of the ceiling top portion 112 a, andis disposed between the inflow port 63 a and the ceiling top portion 112a in the depth direction Z. The bottom projection portion 117 has abottom top portion 117 a which is a tip portion of the bottom projectionportion 117, and even in that configuration, the connecting line PLconnecting the ceiling top portion 112 a and the bottom top portion 117a passes through the bottom side from the partition top portion 111 a.As a result, the partition top portion 111 a is not exposed to theupstream side from the inflow port 63 a.

As a modification D2, the bottom top such as the restriction top portion85 c may be provided on the downstream side of the ceiling top portion112 a. For example, in the modification D1, the bottom top portion 117 ais provided on the downstream side of the ceiling top portion 112 a. Inthe above configuration, the bottom top portion 117 a is disposedbetween the ceiling top portion 112 a and the inflow port 63 a in thedepth direction Z, and the bottom projection portion 117 enters betweenthe ceiling top portion 112 a and the partition top portion 111 a. Forexample, the ceiling projection portion 112 is provided in the inflowport 63 a. Also, in the above configuration, the connecting line PLconnecting the ceiling top portion 112 a and the bottom top portion 117a passes through the bottom side of the partition top portion 111 a. Onthe other hand, the ceiling top portion 112 a does not form the upstreamboundary portion 64 a.

As a modification D3, the connecting line PL may be declined toward thebottom side toward the downstream side. In other words, the connectingangle θa may be a negative value. For example, as shown in FIG. 37, therestriction top portion 85 c is disposed to be spaced apart from thepassage bottom surface 67 more than the ceiling top portion 112 a. Inthe above configuration, the downstream end portion of the upper surface85 b of the inflow restriction portion 85 becomes the restriction topportion 85 c. Further, the inclination direction of the connecting linePL with respect to the depth direction Z is the same as the inclinationdirection of the straight region 115 with respect to the depth directionZ. Also in the above configuration, the partition top portion 111 a isnot exposed to the upstream side from the inflow port 63 a.

As a modification D4, the tip portion, which is the upstream end portionof the flow channel partition portion 111, may have a flat tip end face.For example, as shown in FIG. 38, the tip end face 111 b of the flowchannel partition portion 111 is a flat surface, and the connecting linePL crosses the tip end face 111 b. An end portion of the tip end face111 b opposite to the bottom side is a partition top portion 111 a, anda bottom side end portion 111 c opposite to the partition top portion111 a forms a downstream boundary portion 64 b. In this manner, althoughthe partition top portion 111 a and the downstream boundary portion 64 bdo not coincide with each other, even in this configuration, thepartition top portion 111 a is not exposed to the upstream side from theinflow port 63 a. In that case, for example, a large foreign matter F8that travels linearly along the connecting line PL is likely to bereturned from the measurement flow channel 62 to the passage flowchannel 61 by colliding with the inner peripheral surface of themeasurement flow channel 62 and rebounding even when the large foreignobject F8 once enters the measurement flow channel 62 beyond the flowchannel boundary portion 64. In other words, the large foreign matter F8is likely to exit from the outflow port 63 b.

As a modification D5, the straight region 115 may extend in parallel tothe depth direction Z, similarly to the parallel region 101 of the thirdembodiment. Also in the above configuration, since the connecting linePL and the straight region 115 are relatively inclined, that is, theconnecting angle θa and the straight angle θb are different from eachother, a configuration can be realized in which the partition topportion 111 a is not exposed to the upstream side from the inflow port63 a.

As a modification D6, a part of the tip portion, which is the upstreamend portion of the flow channel partition portion 111, may be exposed tothe upstream side from the inflow port 63 a. In this example, it isassumed that the tip end face of the flow channel partition portion 111is flat or curved, so that a range of the tip portion cannot be clearlyspecified in the flow channel partition portion 111, and the flowchannel boundary portion 64 cannot also be clearly specified.

For example, as shown in FIG. 39, the tip end face 111 b of the flowchannel partition portion 111 and the connecting line PL intersect witheach other. In the above configuration, an intersection angle θc betweenthe connecting line PL and the tip end face 111 b is greater than 90degrees. The tip end face 111 b is a curved surface that is curved so asto protrude toward the upstream side. In this example, a point at whichthe connecting line PL and the tip end face 111 b intersect with eachother is referred to as an intersection Ca, and a tangent line of thetip end face 111 b at the intersection Ca is referred to as a partitiontangent line TL, and the intersection angle θc is an angle of a portionthat is open toward the downstream side between the connecting line PLand the partition tangent line TL.

In the above configuration, for example, as shown in FIG. 40, the largeforeign matter F9 traveling linearly along the connecting line PL islikely to rebound to the bottom side toward the upstream side in theheight direction Y after colliding with the tip end face 111 b of theflow channel partition portion 111. In other words, a large foreignmatter F9 is likely to rebound toward the side opposite to themeasurement flow channel 62. This makes it possible to inhibit that theforeign matter such as the large foreign matter F9 is likely to reboundon the tip end face 111 b and enter the measurement flow channel 62. Onthe other hand, unlike the present modification D6, in the configurationin which the intersection angle θc is less than 90 degrees, it isconsidered that the large foreign matter F9 is likely to rebound towardthe upstream side to the side opposite to the bottom side. In otherwords, it is considered that the large foreign matter F9 enters themeasurement flow channel 62 by rebounding at the tip end face 111 b ofthe flow channel partition portion 111.

As a modification example D7, as shown in FIG. 41, in the configurationin which the tip end face 111 b of the flow channel partition portion111 is a curved surface, the connecting line PL passes through thebottom side from the partition center line Cb of the curvature. In theabove configuration, the tip end face 111 b and the partition centerline Cb extend in parallel to the width direction X, and the flowchannel boundary portion 64 is disposed at a position overlapping withthe virtual line connecting the partition center line Cb and the ceilingtop portion 112 a. In the above configuration, an angle between thetangent line of the tip end face 111 b and the connecting line PL isgreater than 90 degrees at a point where the connecting line PL and thetip end face 111 b intersect with each other, as in the case of themodification D6. For that reason, the foreign matter that travelslinearly along the connecting line PL is likely to travel to theopposite side of the measurement flow channel 62 by rebounding at thetip end face 111 b of the flow channel partition portion 111. For thatreason, the foreign matter can be inhibited from entering themeasurement flow channel 62.

Fifth Embodiment

An air flow meter 50 according to a fifth embodiment has an guidingsurface on which a foreign matter that is likely to travel linearly isbrought toward one wall surface of a pair of wall surfaces in the widthdirection X. In the present embodiment, similarly to the third andfourth embodiments, differences from the second embodiment will bemainly described.

As shown in FIGS. 42 to 44, in the present embodiment, the pair ofpassage wall surfaces 68 in the second embodiment is a pair of passagewall surfaces 68 c and 68 d, and those passage wall surfaces 68 c and 68d correspond to passage facing surfaces. One front passage wall surface68 c is formed by a front cover 51 b and a housing main body 51 a, andthe other back passage wall surface 68 d is formed by a back cover 51 cand the housing main body 51 a. An inner peripheral surface 61 a of thepassage flow channel 61 has a guiding surface 121. The guiding surface121 is included in the inflow ceiling surface portion 66 a, and isprovided in a state of being extended over the pair of passage wallsurfaces 68 c and 68 d, similarly to an inflow restriction portion 85.In the width direction X, one end portion of the guiding surface 121 isdisposed closer to the bottom than the other end. The housing main body51 a corresponds to a partition wall portion that partitions the passageflow channel 61 and the measurement flow channel 62 in the widthdirection X.

In the present embodiment, the guiding surface 121 has an end close tothe front passage wall surface 68 c is disposed to be closer to thebottom side than another end close to the back passage wall surface 68d. In that case, the guiding surface 121 is an inclined surfacegradually away from the bottom surface 67 as the guiding surface 121comes closer to the back passage wall surface 68 d in the widthdirection X. The inclination angle of the guiding surface 121 withrespect to the width direction X is set to, for example, several degreesto several tens of degrees less than 45 degrees. A width dimension ofthe guiding surface 121 in the width direction X is larger than theheight dimension in the height direction Y. The guiding surface 121extends from an inflow port 63 a toward the downstream side, and formssubstantially the entire inflow ceiling surface portion 66 a.

The center line of the passage flow channel 61 is referred to as apassage center line CLa. The passage center line CLa is a virtual lineconnecting the center C1 of the inflow port 63 a and the center C2 ofthe outflow port 63 b (refer to FIG. 42). The center line of themeasurement flow channel 62 is referred to as a measurement center lineCLb. The measurement center line CLb is a virtual line connecting thecenter C3 of the flow channel boundary portion 64 and a center C4 of ameasurement outlet 63 c (refer to FIG. 44). In this example, a virtualline connecting the center C1 of the inflow port 63 a and the center C4of the measurement outlet 63 c is referred to as a flow channel centerline CL, and the flow channel center line CL includes the entire passagecenter line CLa and a part of the measurement center line CLb. The flowchannel center line CL includes a connecting center line CLc as avirtual line connecting the passage center line CLa and the measurementcenter line CLb. The connection center line CLc is connected to thepassage center line CLa by extending from the center C3 of the flowchannel boundary portion 64 toward the upstream side of the passage flowchannel 61.

The inner peripheral surface 62 a of the measurement flow channel 62 hasa measurement ceiling surface 126, a measurement bottom surface 127, anda pair of measurement wall surfaces 128 a and 128 b. The pair ofmeasurement wall surfaces 128 a and 128 b are opposed to each otheracross the flow channel boundary portion 64 and the measurement outlet63 c in the width direction X, and correspond to branch facing surfaces.The front measurement wall surface 128 a is formed by the front cover 51b and the housing main body 51 a, similarly to the front passage wallsurface 68 c, and the back measurement wall surface 128 b is formed bythe back cover 51 c and the housing main body 51 a, similarly to theback passage wall surface 68 d. The front measurement wall surface 128 ahas a width increasing surface 94, and the back measurement wall surface128 b has a width decreasing surface 95. The width increasing surface 94and the width decreasing surface 95 are formed by the housing main body51 a.

The measurement ceiling surface 126 extends from the downstream endportion of the inflow ceiling surface portion 66 a toward the downstreamside of the measurement flow channel 62, and is in a state of beingextended over the inflow ceiling surface portion 66 a and themeasurement outlet 63 c. The measurement bottom surface 127 extends fromthe upstream end portion of the outflow ceiling surface portion 66 btoward the downstream side of the measurement flow channel 62, and is ina state of being extended to the outflow ceiling surface portion 66 band the measurement outlet 63 c. In that case, the measurement ceilingsurface 126 and the measurement bottom surface 127 face each otheracross the measurement wall surfaces 128 a and 128 b.

In the present embodiment, in addition to the width direction X, theheight direction Y, and the depth direction Z, the lateral direction α,the longitudinal direction 13, and the flow channel direction γ are usedto describe the configurations of the passage flow channel 61 and themeasurement flow channel 62. The lateral direction α has only acomponent in the width direction X. In the lateral direction α, a pairof passage wall surfaces 68 c and 68 d are aligned with each other, anda pair of measurement wall surfaces 128 a and 128 b are aligned witheach other. The flow channel direction γ is basically a direction inwhich the passage flow channel 61 and the measurement flow channel 62extend, does not have a component in the width direction X, and has acomponent in the height direction Y and a component in the depthdirection Z. The longitudinal direction 13 is orthogonal to both thelateral direction α and the flow channel direction γ, and has nocomponent in the width direction X, but has a component in the heightdirection Y and a component in the depth direction Z, similarly to theflow channel direction γ. In the longitudinal direction 13, the passageceiling surface 66 and the passage bottom surface 67 face each other,and the measurement ceiling surface 126 and the measurement bottomsurface 127 face each other. The longitudinal direction 13 and the flowchannel direction γ are different from the lateral direction α, andchange at positions of the flow channels 61 and 62 because the passageflow channel 61 and the measurement flow channel 62 are curved.

FIG. 44 shows a diagram in which the passage flow channel 61 and themeasurement flow channel 62 are extended along the flow channel centerline CL with respect to the longitudinal direction β in the regionbetween the inflow port 63 a and the measurement outlet 63 b, when themeasurement bottom surface 127 is viewed from the measurement ceilingsurface 126 side. In FIG. 43, because the flow channel direction γ ofthe inflow port 63 a coincides with the depth direction Z, the widthdirection X coincides with the lateral direction α, the height directionY coincides with the longitudinal direction β, and the depth direction Zcoincides with the flow channel direction γ.

As shown in FIG. 44, the passage flow channel 61 and the measurementflow channel 62 include an inflow region 131 and a lateral region 132,and those regions 131 and 132 extend along the flow channel direction γ.The inflow region 131 is a region in which the inflow port 63 a isprojected in the flow channel direction γ, and extends from the inflowport 63 a toward the measurement outlet 63 c. In the present embodiment,the inflow region 131 extends to the downstream end portion of theintermediate measurement path 92.

The lateral region 132 is disposed side by side in the lateral directionα in the inflow region 131. The lateral region 132 is disposed on theside of the front measurement wall surface 128 a, and the inflow region131 is disposed on the side of the back measurement wall surface 128 b.The lateral region 132 is disposed on the downstream side of the widthincreasing surface 94 in the flow channel direction γ, and does notextend from the inflow port 63 a. For that reason, the lateral region132 does not include a region in which the inflow port 63 a is projectedin the flow channel direction γ. The lateral region 132 is a regionincreased in the measurement flow channel 62, including a portion inwhich the width dimension of each of the width increasing portion 91 aand the intermediate measurement path 92 in the lateral direction α islarger than the width dimension of the upstream-side portion of thewidth increasing portion 91 a in the upstream measurement path 91. Inthe lateral direction α, the width dimension of the inflow region 131 islarger than the width dimension of the lateral region 132. The widthdimension of the inflow region 131 may be the same as or smaller thanthe width dimension of the lateral region 132. In this description, thewidth dimensions of the portions having the largest width dimensions ineach of the inflow region 131 and the lateral region 132 are comparedwith each other.

The upstream measurement path 91 corresponds to an upstream branch path,the intermediate measurement path 92 corresponds to an intermediatebranch path, and the downstream measurement path 93 corresponds to adownstream branch path.

Like the parallel region 101 and the like, the inflow region 131 and thelateral region 132 are virtual regions, and the passage flow channel 61and the measurement flow channel 62 are not actually divided into theinflow region 131 and the lateral region 132. Further, in FIG. 44, theinflow region 131 is illustrated by lighter dot hatching, and thelateral region 132 is illustrated by darker dot hatching.

The flow rate detection unit 52 is disposed in the lateral region 132 inthe intermediate measurement path 92. The measurement board portion 81 ais disposed at a position extending across the inflow region 131 and thelateral region 132 in the lateral direction α so that the substratesurface on which the flow rate detection unit 52 is mounted is includedin the lateral region 132. The flow rate detection unit 52 is disposedat a position not overlapping with the inflow port 63 a in the flowchannel direction γ. In other words, the flow rate detection unit 52 ishidden from the upstream side by a portion forming the width increasingsurface 94 in the housing main body 51 a or the width increasing surface94 in the flow channel direction γ. The measurement board portion 81 amay be disposed in a position in which the entire measurement substrateportion is included in the lateral region 132.

In the flow channel direction γ, a separation distance between the flowrate detection unit 52 and the width increasing surface 94 and aseparation distance between the measurement board portion 81 a and thewidth increasing surface 94 are both smaller than a length dimension ofthe width increasing surface 94. As a result, the measurement boardportion 81 a and the flow rate detection unit 52 are disposed atpositions relatively close to the width increasing surface 94. Aninclination angle of the width increasing surface 94 with respect to theflow channel direction γ is smaller than 45 degrees, for example. Inthat case, since a width dimension of the measurement flow channel 62 inthe lateral direction α does not increase abruptly as the measurementflow channel 62 approaches the intermediate measurement path 92 butgradually increases, turbulence of the air flow such as a vortex is lesslikely to occur in the intake air reaching the lateral region 132.

The guiding surface 121 of the passage flow channel 61 is inclinedtoward the back cover 51 c in a state facing the bottom side, and thusis not orthogonal to the longitudinal direction β. The guiding surface121 is gradually inclined toward the bottom as the inflow ceilingsurface portion 66 a comes closer to the flow channel boundary portion64 as described above, so that the guiding surface 121 is exposedupstream from the inflow port 63 a in the depth direction Z. Therefore,as shown in FIG. 43, when a large foreign matter F10 traveling linearlyin the depth direction Z collides with the guiding surface 121, thetraveling direction of the large foreign matter F10 is changed towardthe back passage wall surface 68 d side and the passage bottom surface67 side with respect to the width direction X and the height directionY. In other words, the traveling direction of the large foreign matterF10 is not a direction parallel to the flow channel direction γ, but adirection inclined with respect to the flow channel direction γ so as toinclude the components of the lateral direction α and the longitudinaldirection β.

Next, the way of how the foreign matter whose traveling direction ischanged by the guiding surface 121 travels will be described withreference to FIG. 45. It should be noted the foreign matter entering themeasurement flow channel 62 from the passage flow channel 61 is anobject to be described hereafter, and therefore a description of achange in the traveling direction of the foreign matter in thelongitudinal direction β will be omitted. In this example, bothsituations where the traveling direction of the foreign matter ischanged and unchanged in the longitudinal direction β are assumed, andin either case, the foreign matter may be traveling along the flowchannel direction γ.

As shown in FIG. 45, when large foreign matter F11, F12 travelinglinearly in the flow channel direction γ collides with the guidingsurface 121, like the large foreign matter F10 described in FIG. 43,both the large foreign matter F11, F12 travel in a direction angled withrespect to the flow channel direction γ toward the back cover 51 c. Inthis example, the large foreign matter F11 collides with the guidingsurface 121 at a position closer to the front cover 51 b in the lateraldirection α, and the large foreign matter F12 collides with the guidingsurface 121 at a position closer to the back cover 51 c. An inclinationangle of the guiding surface 121 with respect to the lateral direction αis relatively small, and this causes the change in the travelingdirection of the large foreign matter F11 and F12 by the guiding surface121 to be relatively small. For that reason, the traveling directions ofthe large foreign matter F11 and F12 are changed by the guiding surface121, and then proceed along a flow of the intake air, so that the largeforeign matter F11 and F12 is likely to coincide with each other in theflow channel direction γ again.

Specifically, the large foreign matter F11 that has collided with theguiding surface 121 proceeds obliquely from the position closer to thefront cover 51 b toward the back cover 51 c, and then proceeds in theflow channel direction γ by gradually changing the traveling directionby the flow of the intake air at a position before reaching the backcover 51 c. In that case, even when the large foreign matter F11 reachesthe intermediate measurement path 92 and is closest to the measurementcircuit board portion 81 a, the large foreign matter F11 passes througha position closer to the back cover 51 c that is relatively distant fromthe measurement board portion 81 a or the lateral region 132 in thelateral direction α. For that reason, even if the traveling direction ofthe large foreign matter F11 slightly changes in the direction facingthe front cover 51 b side, it is difficult for the large foreign matterF1 to enter from the inflow region 131 into the lateral region 132.

On the other hand, unlike the present embodiment, for example, in aconfiguration in which the guiding surface 121 is not provided, thelarge foreign matter F11 passes through a position relatively close tothe measurement board portion 81 a or the lateral region 132 in thelateral direction α as it is as shown by a dashed line in FIG. 45. Forthat reason, even if the traveling direction of the large foreign matterF11 is slightly changed to the direction of the front cover 51 b, thelarge foreign matter F11 is likely to enter the lateral region 132 fromthe inflow region 131. In that case, there is a concern that the largeforeign matter F11 passes between the flow rate detection unit 52 andthe front cover 51 b and adheres to the flow rate detection unit 52.

In addition, the large foreign matter F12 that has collided with theguiding surface 121 at a position closer to the back cover 51 c than thelarge foreign matter F11 travels obliquely toward the back cover 51 c asindicated by a solid line in FIG. 45, collides with the back cover 51 c,and accordingly travels obliquely toward the front cover 51 b.Thereafter, the large foreign matter F12 travels along the flow of theintake air at a position slightly distant from the back cover 51 c,thereby traveling in the flow channel direction γ. Even in that case,even when the large foreign matter F12 reaches the intermediatemeasurement path 92 and is closest to the measurement board portion 81a, as in the case of the large foreign matter F11, the large foreignmatter F12 passes through the position closer to the back cover 51 cwhich is relatively distant from the measurement board portion 81 a orthe lateral region 132 in the lateral direction α.

According to the present embodiment described so far, since the flowrate detection unit 52 is provided in the lateral region 132 which is aregion not projected along the flow channel direction γ from the inflowport 63 a, the foreign matter traveling in the inflow region 131 can beinhibited from reaching the flow rate detection unit 52. In addition,since the guiding surface 121 for bringing the foreign matter away fromthe lateral region 132 in the lateral direction α is provided in thepassage flow channel 61, the foreign matter reaching the intermediatemeasurement path 92 is less likely to pass through a position close tothe lateral region 132. As a result, the foreign matter can be moresurely inhibited from reaching the flow rate detection unit 52.

According to the present embodiment, since the guiding surface 121 isextended over the pair of wall surfaces 128 a and 128 b, in the passageflow channel 61, the foreign matter can be brought in closer to theguiding surface 121 in the entire range in the lateral direction α. Forthat reason, the probability that the foreign matter that has enteredthe measurement flow channel 62 passes through the position close to thelateral region 132 in the lateral direction α can be reduced.

According to the present embodiment, since the guiding surface 121 isdisposed on the upstream side of the flow channel boundary portion 64 inthe passage flow channel 61, the separation distance between the guidingsurface 121 and the lateral region 132 in the flow channel direction γcan be appropriately ensured. In that case, after the travelingdirection of the foreign matter has changed due to the collision of theforeign matter with the guiding surface 121, a distance and a time forthe traveling direction of the foreign matter to coincide with the flowchannel direction γ again by the flow of the intake air can be secureduntil the foreign matter reaches the intermediate measurement path 92.This makes it difficult for the foreign matter to reach the intermediatemeasurement path 92 and enter the lateral region 132 while the travelingdirection of the foreign matter is inclined with respect to the flowchannel direction γ by the guiding surface 121.

According to the present embodiment, the width increasing surface 94included in the front measurement wall surface 128 a is gradually awayfrom the back measurement wall surface 128 b as the width increasingsurface 94 comes closer to the measurement outlet 63 c, thereby formingthe lateral region 132. In that case, for example, as compared with aconfiguration in which the width increasing surface 94 extends inparallel with the lateral direction α, the turbulence such as a vortexflow is less likely to occur in the intake air reaching the lateralregion 132. For that reason, the foreign matter can be inhibited fromentering the lateral region 132 by being entrained in the disturbance ofthe intake air.

According to the present embodiment, the inflow region 131 and thelateral region 132 are reserved by leveraging a difference in thestructure that the upstream measurement path 91 is located between thehousing main body 51 a and the back cover 51 c, while the intermediatemeasurement path 92 is placed between the front cover 51 b and the backcover 51 c. In that case, since there is no need to newly install adedicated member or a dedicated portion for forming the lateral region132 in the housing 51, the structure of the housing 51 is avoided frombecoming complicated, the disturbance of the flow of the intake air bythe dedicated member or the like in the measurement flow channel 62, andthe like can be avoided.

In the present embodiment, a separation distance between the flow ratedetection unit 52 and the width increasing surface 94 in the flowchannel direction γ is smaller than a length dimension of the widthincreasing surface 94. In other words, the flow rate detection unit 52is disposed at a position relatively close to the width increasingsurface 94. In that configuration, when the foreign matter such as thelarge foreign matter F11 and F12 or the like reaches the intermediatemeasurement path 92, the foreign matter immediately passes through theopposite side of the flow rate detection unit 52 across the measurementboard portion 81 a. For that reason, the foreign matter is less likelyto enter the lateral region 132 on the upstream side of the flow ratedetection unit 52.

The fifth embodiment can be applied to various embodiments andcombinations without departing from the scope of the present disclosure.

As a modification E1, the guiding surface 121 may be included in thepassage bottom surface 67 and the passage wall surfaces 68 c and 68 d,instead of being included in the passage ceiling surface 66. Forexample, a configuration in which the guiding surface 121 is included inthe passage bottom surface 67 in a state of being extended over a pairof wall surfaces 68 c, 68 d is applied, or a configuration in which theguiding surface 121 is included in the front passage wall surface 68 cis applied. In the configuration in which the guiding surface 121 isincluded in the front passage wall surface 68 c, the front passage wallsurface 68 c protrudes toward the back passage wall surface 68 d, andthe guiding surface 121 is formed by a surface of the protruding portionon the back passage wall surface 68 d side. Also in that configuration,the traveling direction of the foreign matter colliding with the guidingsurface 121 is temporarily inclined toward the back cover 51 c, so thatthe position of the foreign matter in the lateral direction α can bemoved to a position closer to the back cover 51 c.

As a modification E2, the guiding surface 121 may be provided at aposition downstream of the inflow port 63 a in the passage flow channel61. For example, the guiding surface 121 is provided at an intermediateposition between the inflow port 63 a and the flow channel boundaryportion 64. In that configuration, a part of the inflow ceiling surfaceportion 66 a protrudes toward the bottom side at an intermediateposition between the inflow port 63 a and the flow channel boundaryportion 64, and the guiding surface 121 is formed by the bottom sidesurface of the protruding portion.

As a modification E3, the guiding surface 121 may be included in theinner peripheral surface 62 a of the measurement flow channel 62. Forexample, as shown in FIGS. 46 and 47, the guiding surface 121 isincluded in the measurement bottom surface 127. In that configuration,the guiding surface 121 extends over the pair of measurement wallsurfaces 128 a and 128 b in the lateral direction α. The guiding surface121 extends from the flow channel boundary portion 64 to the widthincreasing surface 94 in the flow channel direction γ, and is formedalmost entirely on the measurement bottom surface 127. In thatconfiguration, as compared with the configuration in which the guidingsurface 121 is included in the inflow ceiling surface portion 66 a as inthe fifth embodiment, the separation distance between the lateral region132 and the guiding surface 121 in the flow channel direction γ isreduced. For that reason, it is assumed that the foreign matter whosetraveling direction is inclined toward the back cover 51 c side by theguiding surface 121 passes through the flow rate detection unit 52 at atiming earlier than when the traveling direction coincides with the flowchannel direction γ. Even in that case, since the entry of the foreignmatter into the lateral region 132 is unlikely to occur, the detectionaccuracy of the flow rate detection unit 52 can be inhibited from beinglowered due to the adhesion of the foreign matter or the like.

Also, in the modification E3, the modifications E1 and E2 may beapplied, and the guiding surface 121 may be included in the measurementbottom surface 127 and the measurement wall surfaces 128 a and 128 b inthe measurement flow channel 62.

As a modification E4, the guiding surface 121 may be disposed on thedownstream side of the flow channel boundary portion 64 in the passageflow channel 61. For example, as shown in FIGS. 48 and 49, the guidingsurface 121 is included in the outflow ceiling surface portion 66 b.Also in the above configuration, as in the fifth embodiment, the guidingsurface 121 is extended over the pair of passage wall surfaces 68 c and68 d. The guiding surface 121 extends from the flow channel boundaryportion 64 to the outflow port 63 b in the flow channel direction γ, andis formed almost entirely on the outflow ceiling surface portion 66 b.

In the above modification E4, a virtual line connecting the center C2 ofthe outflow port 63 b and the center C4 of the measurement outlet 63 cis referred to as an outflow center line CM. The outflow center line CMincludes a return center line CLd as a virtual line connecting thepassage center line CLa and the measurement center line CLb. The returncenter line CLd is connected to the passage center line CLa by extendingfrom the center C3 of the flow channel boundary portion 64 toward thedownstream side in the passage flow channel 61.

In the above configuration, even if the foreign matter traveling throughthe passage flow channel 61 returns to the upstream side and enters themeasurement flow channel 62 due to collision with the outflow ceilingsurface portion 66 b, the position of the foreign matter is easilychanged to a position closer to the back cover 51 c so as to move awayfrom the lateral region 132. For that reason, the foreign matter thathas returned from the outflow port 63 b to the upstream side and hasentered the measurement flow channel 62 is also less likely to passthrough the position close to the lateral region 132 when reaching theintermediate measurement path 92, as in the fifth embodiment.

In the above modification E4, the above-described modifications E1 andE2 may be applied, and the guiding surface 121 may be included in thepassage bottom surface 67 and the passage wall surfaces 68 c and 68 d onthe downstream side of the flow channel boundary portion 64 in thepassage flow channel 61.

As a modification E5, multiple guiding surfaces 121 may be provided. Forexample, as shown in FIG. 50, the guiding surface 121 is included ineach of the inflow ceiling surface portion 66 a, the outflow ceilingsurface portion 66 b, and the measurement bottom surface 127. In theabove configuration, the foreign matter that has entered the measurementflow channel 62 from the upstream side in the passage flow channel 61can be brought in closer to the back cover 51 c by the two guidingsurfaces 121. In addition, both of the foreign matter that has enteredthe measurement flow channel 62 by returning from the downstream side tothe upstream side can be positioned toward the back cover 51 c by thethree guiding surfaces 121. This makes it possible to more reliablyinhibit the foreign matter that has reached the intermediate measurementpath 92 from entering the lateral region 132.

As a modification E6, a covering portion 136 may be provided to coverthe flow rate detection unit 52 from the upstream side. For example, asshown in FIGS. 51 and 52, the cover portion 136 is provided in themeasurement flow channel 62. In the above configuration, the coverportion 136 is disposed at a position spaced downstream from the inflowport 63 a in the flow channel direction γ, and the cover portion 136 isdisposed between the inflow port 63 a and the lateral region 132. Inthat case, the lateral region 132 is hidden downstream of the coveringportion 136 so that the inflow port 63 a is not included in a regionprojected in the flow channel direction γ. In the passage flow channel61 and the measurement flow channel 62, a region formed closer to theinflow port 63 a than the cover portion 136 is referred to as anear-side region 134. The near-side region 134 is disposed laterallywith the lateral region 132 in the lateral direction α in the inflowregion 131.

The cover portion 136 has a cover surface 136 a and an orthogonalsurface 136 b. The cover surface 136 a has a function of guiding theforeign matter advancing toward the downstream side to the back cover 51c, and faces the back cover 51 c side. The cover surface 136 a is aninclined surface that moves away from the back cover 51 c as the coversurface 136 a comes closer to the inflow port 63 a, and is inclined soas to face the inflow port 63 a side with respect to the flow channeldirection γ. In the lateral direction α, a width dimension of the coverportion 136 gradually decreases as the cover portion 136 approaches theinflow port 63 a. The cover portion 136 is included in the housing mainbody 51 a, and the cover surface 136 a is included in the frontmeasurement wall surface 128 a. The inclination angle of the coversurface 136 a with respect to the front cover 51 b is, for example,several degrees to several tens of degrees smaller than 45 degrees.

The orthogonal surface 136 b is orthogonal to the flow channel directionγ and faces the measurement outlet 63 c in the flow channel direction γ.In the flow channel direction γ, the flow rate detection unit 52 isdisposed between the orthogonal surface 136 b and the measurement outlet63 c. The orthogonal surface 136 b extends parallel to the lateraldirection α, but may be inclined with respect to the lateral directionα.

In the above configuration as well, as in the fifth embodiment, when thelarge foreign matter F11 and F12 traveling linearly in the flow channeldirection γ collides with the guiding surface 121, as shown in FIG. 52,both the large foreign matter F11 and F12 travel in a direction inclinedwith respect to the flow channel direction γ toward the back cover 51 c.For that reason, even when the large foreign matter F11 and F12 reachthe intermediate measurement path 92 and is closest to the measurementboard portion 81 a, the large foreign matter F11 and F12 passes througha position in the lateral direction α, which is relatively distant fromthe lateral region 132, from the measurement board portion 81 a. Even ifthe foreign matter such as the large foreign matter F11 advances in thenear-side region 134 instead of the inflow region 131, the foreignmatter is guided to the back cover 51 c side by colliding with the coversurface 136 a. In other words, the foreign matter is guided to aposition away from the lateral region 132 in the lateral direction α.This makes it possible to inhibit the foreign matter advancing in theinflow region 131 and the foreign matter advancing in the near-sideregion 134 from entering the lateral region 132.

As a modification E7, the guiding surface 121 may not bring the foreignmatter closer to the inflow region 131 in the lateral direction α, butmay bring the foreign matter closer to the lateral region 132. In otherwords, the guiding surface 121 may face the front cover 51 b instead ofthe back cover 51 c. In the above configuration, as shown in FIG. 53,when the large foreign matter F11 and F12 traveling linearly in the flowchannel direction γ collides with the guiding surface 121, the largeforeign matter F11 and F12 travels in a direction inclined with respectto the flow channel direction γ toward the front cover 51 b, which isopposite to the fifth embodiment. In that case, the large foreign matterF11 and F12 reaches the cover surface 136 a by traveling through thenear-side region 134 instead of the inflow region 131, and is likely tobe guided to the back cover 51 c side by colliding with the coversurface 136 a. For that reason, the large foreign matter F11 and F12passes through a position relatively far from the lateral region 132,and therefore, the large foreign matter F11 and F12 can be inhibitedfrom entering the lateral region 132.

As a modification F8, the flow rate detection unit 52 may not beseparated from the width increasing surface 94 toward the measurementoutlet 63 c in the flow channel direction γ, but at least a part of theflow rate detection unit 52 may be aligned with the width increasingsurface 94 in the lateral direction α. In that case, since the flow ratedetection unit 52 can be disposed in the immediate vicinity of the widthincreasing surface 94, the foreign matter can be more surely inhibitedfrom entering the lateral region 132 at a position before passingthrough the flow rate detection unit 52 in the inflow region 131.

Sixth Embodiment

An air flow meter 50 according to a sixth embodiment has inflow stepsurfaces 71 a of the second embodiment, a parallel region 101 and aheight narrowing surface 105 of the third embodiment, a configuration inwhich a partition top portion 111 a of the fourth embodiment is notexposed from an inflow port 63 a, and a lateral region 132 of the fifthembodiment. In the present embodiment, differences from the fifthembodiment will be mainly described.

As shown in FIGS. 54 and 55, in the present embodiment, unlike thesecond embodiment, all the inflow step surfaces 71 a are not orthogonalto the depth direction Z, but are inclined with respect to the depthdirection Z. In that case, the inflow step surfaces 71 a are inclinedwith respect to the width direction X, but are not inclined with respectto the height direction Y, and extend parallel to the height directionY. The inflow step surfaces 71 a are inclined so that an end portion ona front passage wall surface 68 c side is disposed at a position closerto the inflow port 63 a than an end portion on a back passage wallsurface 68 d side, and the inflow step surfaces 71 a are inclinedsurfaces facing the inflow port 63 a and the back passage wall surface68 d. The inclination angle of the inflow step surface 71 a with respectto the width direction X is set to, for example, several degrees toseveral tens of degrees smaller than 45 degrees.

The inflow step surfaces 71 a have a function as an guiding surface 121of the fifth embodiment. For example, when a large foreign matter thattravels linearly in the depth direction Z collides with the inflow stepsurfaces 71 a and rebounds, the large foreign matter does not travelparallel to the depth direction Z toward the inflow port 63 a, buttravels toward the back passage wall surface 68 d. In that case, forexample, even if the large foreign matter rebounded at the inflow stepsurfaces 71 a advances in the passage flow channel 61 again toward thedownstream side by the flow of the intake air, the large foreign matteradvances to a position closer to the back passage wall surface 68 d. Asdescribed above, the inflow step surface 71 a corresponds to an guidingsurface, and as shown in FIG. 56, the provision of the multiple inflowstep surfaces 71 a in an inflow ceiling surface portion 66 a correspondsto the provision of the multiple guiding surfaces.

Like the large foreign matter F11 and F12 of the fifth embodiment, thelarge foreign matter traveling in the flow channel direction γ at theposition close to the back passage wall surface 68 d passes through aposition relatively distant from the flow rate detection unit 52 in thelateral direction α even if the large foreign matter reaches anintermediate measurement path 92. For that reason, even if the travelingdirection of the large foreign matter slightly changes in the directionfacing the front cover 51 b, the large foreign matter is unlikely toenter from the inflow region 131 into the lateral region 132.

In the present embodiment, the inflow ceiling surface portion 66 apartitioning the ceiling-side region 102 has an inflow step surface 71a. In that case, the foreign matter that has entered the ceiling-sideregion 102 from the inflow port 63 a is rebounded to the inflow port 63a side at the inflow ceiling surface portion 66 a, thereby inhibitingthe passage of the foreign matter to the downstream side of theceiling-side region 102 in the passage flow channel 61. In addition, theforeign matter that has entered the parallel region 101 from the inflowport 63 a advances linearly in the depth direction Z as it is, so thatthe foreign matter easily comes out from the outflow port 63 b to theoutside. Further, even with respect to the foreign matter that travelslinearly in the direction inclined with respect to the depth directionZ, the partition top portion 111 a is not exposed to the upstream sidefrom the inflow port 63 a, which makes it difficult to directly enterthe measurement flow channel 62 in the state of maintaining the linearlytraveling. Even if there is a foreign matter that has entered themeasurement flow channel 62, the foreign matter is likely to come closerto a position closer to the back cover 51 c by colliding with the inflowstep surfaces 71 a that function as the guiding surface. For thatreason, the foreign matter reaching the intermediate measurement path 92is inhibited from entering the lateral region 132.

The sixth embodiment can be applied to various embodiments andcombinations without departing from the scope of the present disclosure.

As a modification F1, the function as the guiding surface may beimparted to an inflow connection surface 72 a. For example, like theguiding surface 121 of the fifth embodiment, the inflow connectionsurface 72 a may not be orthogonal to the height direction Y, but may bean inclined surface facing the passage bottom surface 67 side and theback cover 51 c side. In addition, the function as the guiding surfacemay be imparted to the outflow step surfaces 71 b or the outflowconnection surface 72 b. As a modification F2, not all of the inflowstep surfaces 71 a may be provided with a function as the guidingsurface, but at least one of the inflow step surfaces 71 a may beprovided with a function as the guiding surface. For example, the inflowstep surface 71 a disposed at the most downstream side of the multipleinflow step surfaces 71 a is inclined with respect to the depthdirection Z, thereby serving as the guiding surface. In the aboveconfiguration, the other inflow step surfaces 71 a are orthogonal to thedepth direction Z and do not have the function as the guiding surface.

A modification F3 may have at least two configurations among the inflowstep surfaces 71 a of the second embodiment, the parallel region 101 andthe height narrowing surface 105 of the third embodiment, theconfiguration in which the partition top portion 111 a is not exposedfrom the inflow port 63 a in the fourth embodiment, and the lateralregion 132 of the fifth embodiment. Even in the above case, a deterrentforce against the foreign matter reaching the flow rate detection unit52 can be exerted.

Although the multiple embodiments according to the present disclosurehave been described above, the present disclosure is not construed asbeing limited to the above-mentioned embodiments, and can be applied tovarious embodiments and combinations within a range not departing fromthe spirit of the present disclosure.

As a modification example G1, in each of the embodiments describedabove, the flow rate detection unit is provided in the measurement flowchannel as the physical quantity detector, but the physical quantitydetector provided in the measurement flow channel may be a humiditydetection unit, a temperature detection unit, or a pressure detectionunit.

As a modification G2, in each of the above-mentioned embodiments, themeasurement flow channel has a circulating shape, but the measurementflow channel may have a shape extending in the depth direction Z withoutcirculating.

Although the present disclosure has been described in accordance withthe examples, it is understood that the disclosure is not limited tosuch examples or structures. The present disclosure encompasses variousmodifications and variations within the scope of equivalents. Inaddition, various combinations and configurations, as well as othercombinations and configurations that include only one element, more, orless, are within the extent and spirit of the present disclosure.

The invention claimed is:
 1. A physical quantity measurement device thatmeasures a physical quantity of a fluid, comprising: a passage flowchannel that includes an inflow port and an outflow port, the fluidentering the passage flow channel through the inflow port and exitingthe passage flow channel through the outflow port; a branch flow channelthat branches off from the passage flow channel; a flow channelpartition portion that separates the passage flow channel and the branchflow channel to have the branch flow channel branch off from the passageflow channel; and a physical quantity detector that detects the physicalquantity of the fluid in the branch flow channel, wherein a pair ofopposing surfaces in an inner peripheral surface of the passage flowchannel face each other across the inflow port and a flow channelboundary portion that is a boundary between the passage flow channel andthe branch flow channel, a direction in which the pair of opposingsurfaces are arranged is defined as a width direction, a directionperpendicular to the width direction and perpendicular to an inflowdirection of the fluid through the inflow port is defined as a heightdirection, a surface of the inner peripheral surface of the passage flowchannel on the same side as the flow channel boundary portion in theheight direction is defined as a ceiling surface, a surface of the innerperipheral surface of the passage flow channel opposite to the ceilingsurface in the height direction is defined as a bottom surface, thepassage flow channel extends along the bottom surface, and the flowchannel partition portion has a partition top portion as anupstream-side end that is not exposed through the inflow port, wherein avirtual line that passes through both a tip portion of a ceilingprojection portion protruding from the ceiling surface toward the bottomsurface and a tip portion of a bottom projection portion protruding fromthe bottom surface toward the ceiling surface on an upstream side of theflow channel boundary portion is defined as a connecting line, whereinthe connecting line causes a connecting angle, which is a virtual angleformed between the inflow direction and the connecting line, facingtoward the ceiling surface, and having the tip portion of the ceilingprojection portion as a vertex, to have a maximum value, and thepartition top portion is located opposite to the bottom surface acrossthe connecting line.
 2. The physical quantity measurement deviceaccording to claim 1, wherein a downstream-side end of a boundarybetween the passage flow channel and the branch flow channel is definedas a downstream boundary portion, and the partition top portion servesas the downstream boundary portion.
 3. The physical quantity measurementdevice according to claim 1, wherein an upstream-side end of the flowchannel boundary portion that is the boundary between the passage flowchannel and the branch flow channel is defined as an upstream boundaryportion, and the tip portion of the ceiling projection portion serves asthe upstream boundary portion.
 4. The physical quantity measurementdevice according to claim claim 1, wherein the tip portion of theceiling projection portion is positioned between the partition topportion and the tip portion of the bottom projection portion in theheight direction.
 5. The physical quantity measurement device accordingto claim 1, wherein an inflow restriction portion that restricts thefluid from flowing into the inflow port by reducing an open area of theinflow port is disposed at the inflow port as the bottom projectionportion.
 6. The physical quantity measurement device according to claim1, wherein a region linearly extending from the inflow port to theoutflow port in the passage flow channel is defined as a straightregion, and the straight region and the connecting line are angledrelative to the inflow direction in opposite directions.
 7. The physicalquantity measurement device according to claim 1, wherein the partitiontop portion is not exposed through the inflow port while a regionlinearly extending from the inflow port to the outflow port exists inthe passage flow channel.
 8. The physical quantity measurement deviceaccording to claim 1, wherein an inflow restriction portion thatrestricts the fluid from flowing into the inflow port by reducing anopen area of the inflow port is disposed in the inflow port to cover thepartition top portion at a position upstream of the partition topportion.
 9. The physical quantity measurement device according to claim1, wherein the flow channel partition portion is provided on adownstream side of the flow channel boundary portion in a depthdirection.
 10. A physical quantity measurement device that measures aphysical quantity of a fluid, comprising: a passage flow channel havingan inflow port and an outflow port, the fluid entering the passage flowchannel through the inflow port and exiting the passage flow channelthrough the outflow port; a branch flow channel that branches off fromthe passage flow channel; a flow channel partition that separates thepassage flow channel and the branch flow channel to have the branch flowchannel branch off from the passage flow channel; and a physicalquantity detector that detects the physical quantity of the fluid in thebranch flow channel, wherein a pair of opposing surfaces in an innerperipheral surface of the passage flow channel face each other acrossthe inflow port and a flow channel boundary portion that is a boundarybetween the passage flow channel and the branch flow channel, adirection along which the pair of opposing surfaces are arranged isdefined as a width direction, a direction orthogonal to the widthdirection and orthogonal to an inflow direction of the fluid through theinflow port is defined as a height direction, a surface of the innerperipheral surface of the passage flow channel on the same side as theflow channel boundary portion in the height direction is defined as aceiling surface, a surface of the inner peripheral surface of thepassage flow channel opposite to the ceiling surface in the heightdirection is defined as a bottom surface, a virtual line that passesthrough both a tip portion of a ceiling projection portion protrudingfrom the ceiling surface toward the bottom surface and a tip portion ofa bottom projection portion protruding from the bottom surface towardthe ceiling surface on an upstream side of the flow channel boundaryportion is defined as a connecting line, wherein the connecting linecauses a connecting angle, which is a virtual angle formed between theinflow direction and the connecting line, facing toward the ceilingsurface, and having the tip portion of the ceiling projection portion asa vertex, to have a maximum value, an angle that is formed between theconnecting line and the flow channel partition portion at anintersection point between the connection line and the flow channelpartition portion and faces away from the branch flow channel is definedas an intersection angle, and the intersection angle is greater than 90degrees.
 11. The physical quantity measurement device according to claim10, wherein the intersection angle is an angle formed between theconnection line and a tangent line of the flow channel partitioningportion at the intersection point between the connection line and theflow channel partitioning portion.
 12. A physical quantity measurementdevice that measures a physical quantity of a fluid, comprising: apassage flow channel that includes an inflow port and an outflow port,the fluid entering the passage flow channel through the inflow port andexiting the passage flow channel through the outflow port; a branch flowchannel that branches off from the passage flow channel; a flow channelpartition portion that separates the passage flow channel and the branchflow channel to have the branch flow channel branch off from the passageflow channel; and a physical quantity detector that detects the physicalquantity of the fluid in the branch flow channel, wherein a pair ofopposing surfaces in an inner peripheral surface of the passage flowchannel face each other across the inflow port and a flow channelboundary portion that is a boundary between the passage flow channel andthe branch flow channel, a direction along which the pair of opposingsurfaces are arranged is defined as a width direction, a directionperpendicular to the width direction and perpendicular to an inflowdirection of the fluid through the inflow port is defined as a heightdirection, a surface of the inner peripheral surface of the passage flowchannel on the same side as the flow channel boundary portion in theheight direction is defined as a ceiling surface, a surface of the innerperipheral surface of the passage flow channel opposite to the ceilingsurface in the height direction is defined as a bottom surface, avirtual line that passes through both a tip portion of a ceilingprojection portion protruding from the ceiling surface toward the bottomsurface and a tip portion of a bottom projection portion protruding fromthe bottom surface toward the ceiling surface on an upstream side of theflow channel boundary portion is defined as a connecting line, whereinthe connecting line causes a connecting angle, which is a virtual angleformed between the inflow direction and the connecting line, facingtoward the ceiling surface, and having the tip portion of the ceilingprojection portion as a vertex, to have a maximum value, the flowchannel partition portion has a partition top portion as anupstream-side end, and the partition top portion is located opposite tothe bottom surface across the connecting line.
 13. The physical quantitymeasurement device according to claim 12, wherein a downstream-side endof a boundary between the passage flow channel and the branch flowchannel is defined as a downstream boundary portion, and the partitiontop portion serves as the downstream boundary portion.
 14. A physicalquantity measurement device configured to measure a physical quantity ofa fluid, comprising: a passage flow channel that includes an inflow portand an outflow port, the fluid entering the passage flow channel throughthe inflow port and exiting the passage flow channel through the outflowport; a branch flow channel that branches off from the passage flowchannel; a flow channel partition portion configured to separate thepassage flow channel and the branch flow channel to have the branch flowchannel branch off from the passage flow channel; and a physicalquantity detector configured to detect the physical quantity of thefluid in the branch flow channel, wherein the flow channel partitionportion has a partition top portion as an upstream-side end, the passageflow channel includes a ceiling surface and a bottom surface that faceeach other in a height direction, the physical quantity measurementdevice further comprises: a bottom projection portion that protrudesfrom the bottom surface toward the ceiling surface; and a ceilingprojection portion that protrudes from the ceiling surface toward thebottom surface, wherein the bottom projection portion and the ceilingprojection portion are disposed at a position upstream of the partitiontop portion to cover the partition top portion such that the partitiontop portion is not exposed through the inflow port.